Method and apparatus for chemical processing

ABSTRACT

A system and method are disclosed after chemical processing involving agitation and/or mixing of components. In one embodiment, the chemical processing involves pressure oxidation and in another embodiment involves pressure leaching. Agitation during chemical processing is aided by an agitator pump disposed in each compartment or stage of a reactor to draw components into a cavity of the agitator pump. In another embodiment, feed to a multi-stage reactor is split between different compartments of reactor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of pending U.S. patentapplication Ser. No. 09/675,598 by Cole entitled “PRESSURE OXIDATION OFSULFIDE GOLD ORES INVOLVING ENHANCED OXYGEN-SULFIDE CONTACT” filed Sep.29, 2000, now U.S. Pat. No. 6,395,063 the entire contents of which areincorporated herein as if set forth herein in full. This applicationclaims a priority benefit under 35 U.S.C. §119(e) to U.S. ProvisionalPatent Application No. 60/236,454 by Cole entitled “METHOD AND APPARATUSFOR CHEMICAL PROCESSING” filed Sep. 29, 2000, the entire contents ofwhich are incorporated herein as if set forth herein in full.

FIELD OF THE INVENTION

The present invention generally relates to pressure oxidation andpressure leaching of metal-containing minerals materials to facilitatemetal recovery, and to other chemical processing operations involvingmixing of or contact between multiple components.

BACKGROUND OF THE INVENTION

Many chemical processing operations involve intimate contact of two ormore components in a reactor. As one example, pressure oxidation ofmetal-bearing mineral materials involves contacting a slurry of themineral material with an oxidant, typically oxygen gas, at elevatedtemperature and pressure to oxidize one or more of the minerals, therebyfreeing metal values of interest for possible recovery in subsequentmetal recovery operations. Pressure oxidation has been used to process avariety of sulfide ores, including both base metal and preciousmetal-containing sulfide ores. Sulfide concentrates prepared fromflotation of such ores have also been processed by pressure oxidation,either alone or in a blend with whole ore material. During pressureoxidation one or more sulfide mineral is oxidized, with sulfide sulfurof the sulfide minerals typically being oxidized to a sulfate form. Thisoxidation results in decomposition of the sulfide minerals and releaseof the metal values. Pressure oxidation operations are typicallyconducted in an acidic environment, such as in the presence of asulfuric acid solution, although some pressure oxidation operations havebeen conducted in an alkaline environment, such as in the presence of ahydroxide or carbonate solution.

In some pressure oxidation operations, the metal(s) are dissolved duringthe pressure oxidation operation and in subsequent metal recoveryoperations the dissolved metals(s) are recovered from solution by avariety of techniques, which may involve, for example, one or more ofselective precipitation, solvent extraction ion exchange andelectrowinning. This will typically be the case when pressure oxidizingbase metal sulfide minerals, such as those containing, for example,nickel, copper, zinc and/or lead. If present, silver is also frequentlydissolved during pressure oxidation operations.

Some metals, however, do not typically dissolve during pressureoxidation operations. For example, when processing sulfide gold ores,the gold typically does not dissolve and remains with solid residue fromthe pressure oxidation operation. The gold may then be recovered, forexample, by leaching the solid residue with a leach solution containinga lixiviant for gold, such as a cyanide or thiosulfate lixiviant. Insulfide gold ores, the gold is typically contained in one or moreiron-containing sulfide mineral, such as for example, pyrite, marcasite,aresenopyrite or pyrrhotite. Direct leaching of gold from these ores,such as direct cyanide leaching, typically results in only very low goldrecovery. For this reason, these sulfide ores are often referred to asrefractory sulfide gold ores. Recovery of gold from these refractorysulfide gold ores typically involves pretreatment of gold-bearingsulfide minerals to decompose at least a portion of the sulfide mineralsto free the gold, thereby facilitating subsequent recovery of the goldby leaching the gold with a leach solution containing cyanide or someother lixiviant. The pretreatment may be performed, for example, on thewhole ore, on a sulfide concentrate resulting from prior flotationoperations, or on a blend of whole ore and ore sulfide concentrate.Pressure oxidation is one pretreatment technique in which thegold-bearing ore and/or concentrate, is contacted with oxygen gas in areactor, called an autoclave, under high pressure to oxidize sulfidesulfur in the sulfide minerals thereby releasing gold for recovery.Typically, the sulfide sulfur is oxidized to a sulfate form in an acidenvironment.

Pressure oxidation operations frequently involve feeding a slurry ofparticulate ore and/or concentrate slurried in an aqueous liquid to thefirst compartment of a multi-stage, or a multi-compartment reactor.Oxygen gas is fed to one or more of the compartments of themulti-compartment reactor to effect the desired oxidation of sulfidesulfur for the purpose of freeing the metals of interest for recovery.As used herein, the terms “multi-stage” and “multi-compartment” are usedinterchangeably in reference to an autoclave, or other reactor,including one or more internal dividers separating the interior reactorvolume into zones that progress in series of the general direction offlow through the reactor, with each such divider acting as at least apartial barrier to flow between adjacent zones. The terms “stage” and“compartment” are used interchangeably herein to refer to such a zonewithin a multi-stage reactor.

A significant expense associated with pressure oxidation is the cost ofproviding oxygen gas for use in the reactor. There is often significantinefficiency in the use of oxygen gas and it is, therefore, commonpractice to feed to the reactor a significant excess of oxygen gas overthat stoichiometrically required for sulfide sulfur oxidation, with theexcess oxygen gas being essentially wasted. Moreover, the oxygen gas istypically fed to the reactor in a gas stream that is substantiallyenriched in oxygen compared to air. Providing such a purified stream ofoxygen gas typically requires building and operating an oxygen plant toprepare an oxygen-enriched gas stream from air, such as for example bymembrane or cryogenic separation techniques, which is expensive.

Another frequent problem with current pressure oxidation operations isthermal inefficiency in the reactor. Oxidation of the sulfide mineralsis exothermic, but maintenance of a minimum elevated temperature isrequired to attain acceptable reaction kinetics. Therefore, in manyinstances heat, often in the form of steam, is added to the firstcompartment of a multi-stage reactor to maintain an adequate temperaturein the first stage, where the oxidation reaction is initiated.Conversely, in one or more subsequent stage of the reactor, it is oftennecessary to add water to prevent the occurrence of excessively hightemperatures, with the quantity of water required increasing as moresteam is added to the first compartment.

The addition of steam in the front-end of the reactor is undesirablebecause of the cost of generating the steam. Also, as the steamcondenses in the reactor it reduces the density of solids in a slurryand, therefore, the quantity of ore that may be processed through thereactor per unit time. The addition of water in the back-end of thereactor is likewise undesirable because the added water also dilutes theslurry and reduces the density of solids in the slurry, thereby furtherreducing potential ore through-put.

Another example of a chemical processing operation that involvesintimate contact between multiple components is pressure leaching.Pressure leaching involves contacting a metal-containing material with aleach solution to dissolve at least a portion of one or more metal ofinterest. The pressure leaching is conducted in a reactor at elevatedtemperature and pressure to improve leach kinetics. Although the fieldof pressure leaching is not confined to mineral processing operations,many metal-bearing ores, and concentrates prepared by flotation of suchores, are processed by pressure leaching to dissolve one or more metalsof interest into the leach solution. Mineral materials susceptible toprocessing by pressure leaching are typically oxide ores, andconcentrates prepared from such ores. Unlike pressure oxidation, it isnot necessary to oxidize a sulfide mineral to release the metals.Rather, the metals are directly leachable from the mineral material ofinterest. The leach solution used for pressure leaching may be acidic oralkaline, depending upon the materials involved and the specificcircumstances. For example, either alkaline (e.g., ammoniacal) or acidic(e.g., sulfate) leach solutions may be used to pressure leach nickel orcobalt from laterite or saprolite ores. As another example, copper,platinum, palladium and gold may be pressure leached from oxide oresusing an alkaline (e.g., ammoniacal) or an acidic (e.g., chloride) leachsolutions. As a further example, tungsten and molybdenum may be pressureleached from oxide ores using alkaline leach solutions (e.g., solutionsof sodium carbonate or sodium hydroxide). Moreover, zinc, uranium,vanadium and manganese may be pressure leached from oxide ores usingacidic (e.g., sulfate) solutions. Furthermore, light metals, such asaluminum, may be pressure leached from oxide ores, such as bauxite ores,using an alkaline leach solution (e.g., sodium hydroxide solution).

A common feature of these and other pressure leaching processes is thatit is generally desirable that the particulate mineral material beevenly dispersed throughout and intimately mixed with leach solution,and to actively agitate the mixture to promote enhanced contact a forimproved leach kinetics. Agitation and mixing in current pressureleaching operations, however, could be more effective, especially inoperations involving a highly viscous medium, as is typically the casewith mineral processing operations.

In addition to pressure oxidation and pressure leaching operations, manyother chemical processing operations involve agitation or mixing. Thiswould be the situation, for example, in reaction systems involvingdispersion of a gas phase throughout a liquid or a slurry, mixing ofmultiple liquids or mixing solids and liquid in a slurry. In these andother chemical processing operations, it would often be advantageous toconduct the operation with more efficient mixing of these materials,especially in high viscosity systems in which it can be particularlydifficult to achieve and/or maintain a homogenous mixture.

There is a need for improved chemical processing techniques involvingmixing of materials and apparatus for use therein. There is especially aneed for pressure oxidation processes that more efficiently utilizeexpensive oxygen gas fed to the reactor and/or that operate in a morethermally efficient manner.

SUMMARY OF THE INVENTION

The present invention generally relates to chemical processingoperations, and more particularly to such operations in which it isdesirable to mix or otherwise agitate the contents within the internalreactor volume of a chemical reactor. Two particularly importantapplications for the present invention include pressure oxidation andpressure leaching applications, although the features of the presentinvention are equally applicable to other chemical processing operationsas well. With respect to pressure oxidation and pressure leachingapplications, the material being processed will generally involve aparticulate mineral material feed, typically slurried in an aqueousliquid. The mineral material feed includes at least one metal value. Asused herein, metal value refers to a metal component or componentstargeted for recovery from the mineral material feed. Such a mineralmaterial feed may include a whole ore, an ore concentrate prepared fromprior flotation operations, or a blend of the two. Also, the mineralmaterial feed may be or include tailings or other solid residue fromprior mineral processing operations. One preferred application for thepresent invention is in pressure oxidizing gold-bearing mineral materialfeed to free gold from association with at least one sulfide mineralwith which gold is associated. Mineral material feed to the reactor canbe any gold-bearing material containing gold in association with atleast one sulfide material, for which it is desirable to decompose atleast a portion of the sulfide mineral to facilitate gold recovery.These gold-bearing mineral materials are referred to as refractorysulfide materials when a significant portion of the gold cannot berecovered by direct leaching of the mineral material with a lixiviantfor gold, such as by leaching with a cyanide, thiosulfate or otherlixiviant. With the present invention, it has been found that reactorperformance, and especially oxygen gas utilization efficiency, is oftensignificantly improved during pressure oxidation of these gold-bearingrefractory sulfide materials. In one application, the metal value of themineral material includes one or more metal component in addition togold. The other metal value could include any metal component insufficient quantity to justify recovery. Examples of possible metals forsuch additional metal component include copper, nickel, zinc, lead,cobalt, vanadium, tungsten, molybdenum and silver. During pressureoxidation such an additional metal component would typically bedissolved into the liquid phase in the reactor, while the gold wouldremain in the solids. One preferred application involves pressureoxidation of gold-bearing copper sulfide mineral materials, with copperbeing recovered from the liquid phase and gold from solids dischargedfrom the reactor. One preferred technique for recovering the copper isby solvent extraction.

A first aspect of the present invention generally relates to agitationof a mineral material slurry in a reactor in which a pressure oxidationoperation or a pressure leaching operation is being effected tofacilitate recovery of one or more metal components of interest. Themineral material feed is introduced into the reactor in a manner sothat, in the reactor, the mineral material is in a slurry, typicallywith water or another aqueous liquid. In the case of pressure leaching,the liquid will typically be either acidic or alkaline leach liquidchosen to leach the metal(s) of interest from the mineral material feed.In the case of pressure oxidation, oxygen gas, typically under highpressure, is also introduced into the reactor for use as an oxidant tooxidize at least a portion of sulfide sulfur in the mineral material,thereby freeing one or more metal of interest for possible subsequentmetal recovery operations. As previously noted, in pressure oxidationand pressure leaching operations, the reactor is typically referred toas an autoclave.

According to the first aspect of the invention, slurry present in thereactor is agitated during pressure oxidation by at least one agitatordisposed in the reactor and operated to provide a pumping action inwhich portions of the slurry are continually drawn into and expelledfrom a cavity in the agitator. This pumping action is typically effectedthrough rotation of at least a portion of the agitator in a manner toexpel the slurry from the cavity in a generally radially outwarddirection, thereby creating a fluid suction within the cavity to drawadditional slurry into the cavity for continuous cycling of slurrythrough the agitator while the rotation is continued.

Various refinements exist for features noted in relation to this firstaspect of the present invention, and additional features may also beincorporated as well. These refinements and additional features may beincorporated individually or in any combination. In one refinement, theagitator has a fluid intake that is preferably axially aligned with acenter of the noted cavity, and the agitator further has an axis ofrotation that is aligned with the center of the cavity. Additionalrefinements involve directing a flow of the mineral material feed(and/or the oxygen gas in the case of pressure oxidation) toward a fluidintake of the agitator through which slurry is directed to the cavity.In a preferred embodiment, one or both of these flows are directed in avertically upward direction toward the fluid intake. In one embodimentinvolving pressure oxidation, a flow of oxygen gas is introduced intothe slurry within the reactor from an oxygen gas supply line insubstantially vertical orientation located below the fluid intake sothat oxygen gas exiting the oxygen gas supply line flows in asubstantially vertically upward direction toward the fluid intake andthe flow of mineral material feed is also directed in an upwarddirection toward the fluid intake, in a manner preferably designed sothat the flow of mineral material feed intersects the corresponding flowof oxygen gas in the vicinity of the fluid intake. In the case ofpressure oxidation, using these refinements, in combination with thepumping action of the agitator, dispersion of the oxygen gas throughoutthe slurry and dissolution of the oxygen gas into the slurry liquid arepromoted, with a result that more efficient utilization of the oxygengas to oxidize sulfide sulfur is typically achievable within thereactor.

It should be appreciated that the pressure oxidation or pressureleaching conducted in accordance with this first aspect of the inventionwill typically be performed in a multistage reactor (also referred tointerchangeably as a multi-compartment reactor), with oxygen gas (in thecase of pressure oxidation) typically being introduced into each of thestages (or compartments). Moreover, and as will be discussed in moredetail below in relation to a second aspect of the present invention,mineral material feed may advantageously be introduced into more thanone of the reactor stages to further enhance performance.

In one embodiment of the first aspect of the invention, the cavity ofthe agitator is defined between a pair of spaced, typically verticallyspaced, partitions of an agitator pump. In one embodiment, the first andsecond partitions are disposed in at least substantially horizontalrelation, with the entire first partition being disposed at a lowerelevation than the entirety of the second partition. Other orientationscould possibly be utilized for the first and/or second partitions. Anaperture is formed in the first partition such that slurry in thereactor is drawn into the cavity of the agitator through the aperture.The aperture may be the fluid intake of the agitator through whichslurry is drawn to supply the cavity. In one refinement, however, theagitator includes a pump inlet conduit or the like to provide a flowpath through which slurry is drawn to be directed through the apertureand into the cavity. In this case, the fluid intake to of the agitatorwould be an open end of the pump inlet conduit, or the like, throughwhich slurry is initially drawn into the agitator for fluidcommunication to the cavity. In one preferred embodiment, the pump inletconduit projects at least generally downwardly toward the bottom of thereactor in an at least substantially vertical orientation and/or inaxial alignment with the direction in which the flow of oxygen gas isintroduced into the slurry in the reactor. Other configurations for thefluid intake of the agitator are also possible. Moreover, in the case ofpressure oxidation, whether or not the agitator includes a pump inletconduit, or the like, in a further refinement the oxygen gas ispreferably introduced into the reactor at a location which is “close” tothe fluid intake of the agitator. In one embodiment for pressureoxidation processing, the spacing between a discharge end of an oxygeninlet line and the corresponding fluid intake of the agitator is nolarger than about 6 inches.

As noted, a pumping action of the agitator, wherein slurry iscontinuously drawn into and expelled from the cavity during operation ofthe agitator, is typically effected by rotation of at least a portion ofthe agitator. For example, the agitator may include a plurality of vanesthat are rotated within the slurry in the reactor during pressureoxidation. The vanes typically extend in a direction generally radiallyoutward and away from the cavity. When rotated about an axis of rotationextending substantially through the center of the cavity, the vanes helpto expel fluid from the cavity in a generally radially outward directionand create a fluid suction to draw additional slurry into the cavity,thereby creating a pumping action. Shear at the outward edges of therotating vanes, in combination with the pumping action of the agitator,is believed to enhance effective mixing of components and, in the caseof pressure oxidation, dispersion of the oxygen gas throughout theslurry to promote efficient use of oxygen to oxidize sulfide sulfur. Inone embodiment, the vanes are incorporated into the agitator so thateach vane extends in a vertical direction at least between the first andsecond partitions (i.e., a portion of each vane may extend verticallybeyond the first and/or second partition) and in a generally radiallyoutward direction beyond the perimeter of the first partition and/orsecond partition. The vanes may each extend generally radially inward ofa perimeter of the inlet aperture within the first partition in oneembodiment (i.e., a portion of each vane may be disposed “over” theinlet aperture). Alternatively, the vanes may each terminate in agenerally radially inward direction at a location not within a perimeterof the inlet aperture (i.e., no portion of the vanes is disposed “over”the inlet aperture).

A second aspect of the present invention generally relates to the mannerin which mineral material feed is introduced into a reactor for pressureoxidation or pressure leaching, with mineral material feed beingseparately introduced at least two different locations within thereactor. At least a first flow of mineral material feed, typically in aslurry with an aqueous liquid, is introduced into the reactor at a firstlocation (e.g., into a first compartment of a multi-stage reactor). Atleast a second flow of mineral material feed, also typically in a slurrywith an aqueous liquid, is introduced into the reactor at a secondlocation, which is spaced from the first location (e.g., into a secondcompartment of a multi-stage reactor). In a further embodiment of thissecond aspect of the invention, in the case of pressure oxidation, aflow of oxygen gas is directed into each of the compartments of amulti-stage reactor. In any case, slurry within the reactor is agitatedfor enhanced homogenization of the slurry and to promote intimatecontact between reactants, preferably with each compartment of thereactor being independently agitated by at least one agitator disposedwithin each compartment.

Various refinements exist for features noted in relation to this secondaspect of the present invention and additional features may also beincorporated as well. These refinements and additional features may beincorporated individually or in any combination. In one refinement, atleast one of, and more preferably both of, the first and second flows ofmineral material feed, are introduced into the reactor in an at least agenerally upward direction (e.g., such that the flows are projected atan upward angle). Also, significant refinements are achievable through acombination of using the agitation of the first aspect of the inventionin the vicinity of at least one, and preferably both, of the first andsecond flows of mineral material feed. For example, the agitation of thefirst aspect, optionally including any refinements thereto, may beadvantageously implemented in first and second compartments of amulti-stage reactor in combination with the split mineral material feedof the second aspect of the invention. Portions of total mineralmaterial feed to the reactor may be allocated between the first andsecond flows of mineral material feed in any desired manner. However,for enhanced performance it is generally preferred that at least about25% of the total mineral material feed to the reactor be allocated toeach of the first and second flows, and more preferably at least about50% of total mineral material feed to the reactor is allocated to thefirst flow. In one embodiment, the total mineral material feed is splitapproximately equally between the first and second flows.

As noted, the reactor will often be a multi-stage reactor. Such areactor has a plurality of stages, or compartments, arranged in series.One preferred reactor for use with the present invention includes fourcompartments. Flow in such a multi-compartment reactor proceeds from thefirst compartment in series to the second compartment in series, and soon through the last compartment in series. The processed slurry is thentypically discharged from the last, or most downstream, compartment.These compartments are at least partially isolated from each other by adivider disposed between adjacent compartments in series. In oneembodiment, slurry moves from one compartment to the next succeedingcompartment in series by overflowing the divider or passing through arestricted opening through or adjacent to the divider. The divider istypically a wall or other partition, such as of metal construction. Inone embodiment of the invention, the first flow of mineral material feedis introduced into the first compartment in series and the second flowof mineral material feed is introduced into the second compartment inseries.

In the case of pressure oxidation, conventional operation is tointroduce mineral material feed into only the first in series of thecompartments, with oxygen gas typically being added to each of thecompartments, so that the oxidation of sulfide minerals proceeds to agreater extent as the slurry moves from compartment to compartmentthrough the reactor. In a preferred embodiment of pressure oxidation ofthe present invention, however, mineral material feed is introduced intoat least each of the first and the second compartments in series, andintroduction of oxygen gas is adjusted accordingly. This has been foundadvantageous from both the perspectives of thermal efficiency and oxygenutilization. In conventional pressure oxidation, when mineral materialfeed is introduced only into the first compartment, heat generated inthe first compartment from the exothermic oxidation reaction is notsufficient for autothermal operation, and it is therefore oftennecessary to add heat, typically in the form of steam, to the firstcompartment to maintain the first compartment at a sufficiently hightemperature. In later compartments, however, as the oxidation reactionprogresses, cooling is often required to avoid excessive temperatures.Such cooling is often accomplished by adding water in one or more of thelater compartments. The effect of adding steam in the first compartmentand water in later compartments is that the density of the slurry in thereactor is reduced, and therefore also throughput of mineral material isreduced.

By splitting the mineral material feed between the first compartment andthe second compartment during pressure oxidation, less steam is requiredin the first compartment due to a reduction in feed to the firstcompartment that must be heated to reaction temperature. Furthermore,the retention time in the first compartment is increased, which in turnincreases the extent to which sulfides are oxidized in the firstcompartment, resulting in higher heat production in the firstcompartment per unit of mineral material feed to the first compartmentand further reducing steam requirements in the first compartment. Hotslurry flowing from the first compartment into the second compartmentoften provides sufficient heat to maintain the temperature in the secondcompartment at the desired elevated reaction temperature, even with theintroduction of the second flow of mineral material feed into the secondcompartment. In some instances, it may be desirable to provide somesupplemental heating from an outside heat source, such as by steamaddition. Even if such supplemental heating is required in the secondcompartment, the total supplemental heat to the reactor will typicallybe significantly lower than required in the conventional situation, inwhich mineral material feed is introduced into only the firstcompartment. Performance in specific instances will depend, of course,upon the sulfide sulfur content of the mineral material being processedand the specific conditions under which the pressure oxidation is beingoperated. An additional benefit from splitting total mineral materialfeed between first and second compartments is that it is often alsopossible to reduce water additions to prevent excessive temperatures indownstream compartments. Furthermore, the enhanced thermalcharacteristics in the first and second compartments are believed topromote efficient utilization of oxygen gas fed at the reactor duringpressure oxidation.

In a particularly preferred implementation of the invention, the firstand second aspects are combined. For example, mineral material feed maybe introduced into the first two compartments of a multi-stage reactoraccording to the second aspect of the invention, and the agitation ofthe first aspect may beneficially be implemented in the first and/orsecond compartments, and optionally also in other compartments. In thecase of pressure oxidation, by reducing steam and water additions bysplitting the mineral material feed between compartments, it istypically possible to process a higher density slurry through thereactor, while the pumping agitation promotes efficient utilization ofoxygen gas to adequately oxidize sulfide minerals in the higher densityslurry.

In the case of pressure oxidation, with each of the first and secondaspects of the present invention, oxygen gas is typically introducedinto multiple compartments, and preferably into each of the compartmentsof a multi-stage reactor. However, a greater portion of total oxygen gasfed to the reactor is typically introduced into each compartment intowhich mineral material feed is introduced, and a lesser portion isintroduced into each compartment in which no mineral material feed isintroduced. In the case of the second aspect of the invention, when themineral material feed is split between compartments, it is preferredthat the relative quantities of oxygen gas introduced into each of thosecompartments be approximately in proportion to the relative quantitiesof mineral material feed introduced into each of those compartments. Forexample, when 50% of the total mineral material feed is introduced intoeach of the first and second compartments during pressure oxidation,oxygen gas feed to each of the first and second compartments should beapproximately equal, with perhaps about 45% of the total oxygen gasbeing fed to each of those compartments and the third and fourthcompartments each receiving perhaps only 5% or less of the total oxygengas.

A third aspect of the present invention generally relates to the mannerin which the slurry is agitated within a reactor during pressureoxidation or pressure leaching operations. This system includes amineral material feed system for providing a mineral material feed to areactor, and an appropriate metal recovery system to receive reactordischarge from the reactor for the purpose of recovering one or moremetal from the reactor discharge. In the case of pressure oxidation of agold-bearing refractory material, the metal recovery system involvesoperations for recovering gold from solid residue of the reactordischarge (e.g., via cyanide, thiosulfate or other leaching of thegold). The reactor includes a pressure vessel having a plurality offluid connections. There is at least one mineral material feed inlet forintroducing mineral material feed into the pressure vessel and at leastone discharge outlet for discharging processed slurry from the pressurevessel. In the case of pressure oxidation, the reactor also includes atleast one oxygen gas feed inlet for introducing oxygen gas into thepressure vessel from an appropriate oxygen supply system, and theprocessed slurry will be an oxidized slurry.

The reactor of this third aspect of the invention also includes at leastone agitator pump, of the type previously noted with respect to thefirst aspect of the invention, disposed at least partially inside of thepressure vessel. This agitator pump typically includes a drive shaft, apair of vertically spaced first and second partitions, and a pluralityof vanes. Preferably, at least a portion of at least one, and morepreferably each of, these vanes interfaces with and extends between thefirst and second partitions. The first partition includes at least oneinlet aperture which effectively defines an inlet to the space betweenthe first and second partitions, or stated another way this inletaperture defines a pump inlet.

Various refinements exist for the features noted in relation to thisthird aspect of the present invention and further features may also beincorporated in this third aspect of the present invention as well.These refinements and additional features may exist individually or inany combination. The reactor may have multiple stages. Preferably, atleast one agitator pump is used in each of these stages. By includingmultiple stages, the various combinations of features discussed above inrelation to the second aspect of the present invention may be used incombination with this third aspect of the present invention as well(e.g., simultaneously introducing the mineral material feed into atleast two different compartments of a multi-stage reactor).

The vanes associated with the third aspect of the invention need not beconfined to the space between the first and second vertically spacedpartitions. For instance, the vanes may extend radially beyond aperimeter of one or more of the first and second partitions, the vanesmay extend vertically beyond the first partition in a direction which isat least generally away from the space between the first and secondpartitions, the vanes may extend vertically beyond the second partitionin a direction which is at least generally away from the space betweenthe first and second partitions, or any combination thereof. Any portionof the vanes which extends vertically beyond the first and/or secondpartition in a direction which is at least generally away from the spacebetween the first and second partitions may be disposed entirelyradially beyond a perimeter of the adjacentmost partition or may bedisposed in at least partial vertical alignment with the adjacentmostpartition (e.g., by disposing the first and/or second partition within anotch or the like which is formed in the vanes).

The spacing between the first and second partitions may be characterizedas defining a pump cavity, of sorts, and which is accessed by the inletaperture in the first partition. In one embodiment the first and secondpartitions are each disposed in at least substantially horizontalrelation, with the first partition being disposed at a lower elevationthan the second partition. The inlet aperture in this case projectstoward a bottom of the pressure vessel. In one embodiment a pump inletconduit interfaces with the first partition in alignment with the firstinlet aperture and extends at least generally downwardly toward thebottom of the reactor, preferably in at least substantially verticalrelation.

In the case of pressure oxidation, oxygen gas that is introduced intothe pressure vessel is preferably directed at least generally upwardlyand toward a fluid intake of the agitator. More preferably, an oxygengas supply line is axially aligned with a center of the inlet apertureand/or the inlet conduit in a vertical orientation. Similarly,preferably the mineral material feed that is being introduced into thepressure vessel of the reactor is directed at least generally upwardlyand toward the fluid intake of the agitator. Disposing an oxygen gasdischarge line and a corresponding mineral material feed discharge linesufficiently close to a fluid intake further promotes intimate mixing ofoxygen gas and mineral material via the agitator pump. In oneembodiment, a vertical spacing between the discharge end of the oxygengas supply line and the fluid intake of the agitator is preferably morethan about 6 inches.

A fourth aspect of the present invention generally relates to the mannerin which mineral material feed is introduced into a reactor for pressureoxidation or pressure leaching. This system includes a mineral materialfeed system for providing mineral material feed to a reactor and anappropriate metal recovery system to receive reactor discharge forpurposes of recovering one or more metal form the reactor discharge. Thereactor includes a pressure vessel having at least two compartments. Atleast one agitator is disposed in each of first and second compartments.There is at least a first mineral material feed inlet for introducingmineral material feed directly into the first compartment of thepressure vessel, and there is at least a second slurry feed inlet forintroducing mineral material feed directly into the second compartmentof the pressure vessel, preferably simultaneously with the introductionof mineral material feed into the first compartment. There is also atleast one discharge outlet for discharging processed slurry from thepressure vessel to be received by the metal recovery system. In the caseof pressure oxidation, the pressure vessel also includes at least oneoxygen gas inlet for introducing oxygen gas into the pressure vesselfrom an appropriate oxygen gas supply system.

Various refinements exist for the features noted in relation to thisfourth aspect of the present invention and further features may also beincorporated in fourth aspect of the present invention as well. Theserefinements and additional features may exist individually or in anycombination. The mineral material feed may be introduced into one orboth of the first and second compartments in a generally verticallyupward direction of flow, generally directed at a correspondingagitator. In one embodiment, a first mineral material feed supply lineextends within the pressure vessel along at least a portion of thebottom thereof and includes a discharge end portion that extends awayfrom the bottom to direct the first flow of mineral material feed intothe first compartment, and a second mineral material feed supply lineextends within the pressure vessel along at least a portion of thebottom thereof and includes a discharge end portion that extends awayfrom the bottom to direct the second flow of mineral material feed intothe second compartment. Any design for providing the first mineralmaterial slurry to each of these first and second mineral material feedsupply lines may be utilized. For instance, a single main supply linecould penetrate the pressure vessel and be directed along the bottomportion of the pressure vessel and the first and second mineral materialfeed supply lines could extend upwardly therefrom. Also, those variouscombinations of features discussed above in relation to the third aspectof the present invention may also be utilized by the subject fourthaspect of the present invention.

A fifth aspect of the present invention generally relates to the mannerin which mineral material feed is introduced into a reactor for pressureoxidation or pressure leaching.

This system includes a mineral material feed system for providingmineral material feed to a reactor and an appropriate metal recoverysystem to receive reactor discharge for purposes of recovering one ormore metal from the reactor discharge. The reactor includes a pressurevessel having at least one compartment, and preferably at least twocompartments. At least one agitator is disposed in each such compartmentof the reactor. There is at least one mineral material feed inlet forintroducing the mineral material feed into the reactor in a generallyupward direction, preferably directed generally upward in a directiontoward an agitator. There is also at least one discharge outlet fordischarging processed slurry from the pressure vessel to be received bythe recovery system. In the case of pressure oxidation, the pressurevessel also includes at least one oxygen inlet for introducing oxygeninto the pressure vessel from an appropriate oxygen supply system foreffecting the pressure oxidation operation.

Various refinements exist for the features noted in relation to thisfifth aspect of the present invention and further features may also beincorporated in the subject fifth aspect of the present invention aswell. These refinements and additional features may exist individuallyor in any combination. Those various combinations of features discussedabove in relation to the third aspect of the present invention may beutilized by the subject fifth aspect of the present invention.Similarly, those various combinations of features discussed above inrelation to the fourth aspect of the present invention may be utilizedby the subject fifth aspect of the present invention as well.

A sixth aspect of the invention generally relates to mixing multiplecomponents of a flowable medium, in which the agitating aspect of theinvention is applied generally to mix a contained volume of such aflowable medium.

A seventh aspect of the invention generally relates to dispersing amaterial in a flowable medium, in which the agitating aspect of thepresent invention is applied generally to disperse a material introducedinto a contained volume of such a flowable medium.

An eighth aspect of the invention generally relates to dispersing areactant in a flowable medium, in which the agitating aspect of thepresent invention is applied generally to disperse in a contained volumeof a flowable medium a chemical reactant introduced into the flowablemedium.

A ninth aspect of the invention generally relates to a chemical reactorthat implements an agitator to agitate contents that may be containedwithin the internal reactor volume.

Moreover, any of the features of any of these or other aspects of theinvention discussed herein may be combined in any compatible combinationwith any other of features of any other aspect or aspects of theinvention.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a schematic of one embodiment of a mineral processing systemwhich may utilize one or more aspects of the present invention.

FIG. 2 is a schematic showing one embodiment of a pressure oxidationreactor, or autoclave, that may be utilized with the mineral processingsystem of FIG. 1, and which includes various aspects of the presentinvention.

FIG. 3 is a perspective view of one embodiment of an agitator pump whichmay be used by the pressure oxidation reactor of FIG. 2, and which is inaccordance another aspect of the present invention.

FIG. 4 is a bottom view of the agitator pump of FIG. 3.

FIG. 5 is a cross-sectional view of the agitator pump of FIG. 3, takenalong line 5—5.

FIG. 6 is an end view, looking at least generally radially inwardly, ofan alternative embodiment of a vane which may be utilized by theagitator pump of FIG. 3.

FIG. 7 is a cross-sectional view of the vane of FIG. 6.

FIG. 8 is a side view of an agitator used to generate data for Example1.

FIG. 9 is a schematic of a reactor showing the configuration forintroducing oxygen gas and mineral material feed for Example 1.

FIG. 10 is a schematic of a reactor showing the configuration forintroducing oxygen gas and mineral material feed for Example 2.

FIG. 11 is a schematic of a reactor showing the configuration forintroducing oxygen gas and mineral material feed for Example 3.

FIG. 12 is a cross-sectional view of the agitator pump of FIG. 7, takenalong line 12—12.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described in relation to the accompanyingdrawings which at least assist in illustrating its various pertinentfeatures. A block flow diagram of one embodiment of a mineral processingsystem 2 is generally illustrated in FIG. 1, and which may be utilizedfor executing both batch and continuous processing operations, as wellas any hybrid thereof The mineral processing system 2 includes a mineralmaterial supply system 6 which provides a supply of an appropriatemineral material slurry to a reactor 26, typically in the form of acontinuous flow. There are a number of key features which may beimplemented by the reactor 26, alone or in combination, and which willbe discussed in more detail below in relation to FIGS. 2-7.

The operation performed on the mineral material in the reactor 26 is inpreparation of metal recovery in a metal recovery system 82. Theoperation performed in the reactor 26 may be, for example, pressureoxidation to free one or more metals from sulfide minerals in mineralmaterial feed. As another example, the operation performed in thereactor 26 may be pressure leaching of the mineral material to dissolveone or more metal of interest into a leach solution. In any event, adischarge from the reactor 26 is directed to the metal recovery system82, where at least one metal of interest is recovered from thedischarge. Any type of metal recovery technique/apparatus may beutilized by the metal recovery system 82 that is appropriate for themetal of interest. For example, when recovering gold from solid residuedischarged from the reactor 26, the metal recovery system 82 may,include lixiviation of the gold with a leach solution including adissolved cyanide, thiosulfate or other lixiviant for gold, which may befollowed by an electrowinning or some other technique for preparing apurified gold product. As another example, the metal(s) of interest maybe dissolved in a liquid phase discharged from the reactor, as is thecase, for example, with pressure oxidation of base metals and pressureleaching. Any of a variety of operations may be performed during therecovery of the metal(s) of interest from solution, including one ormore of ion exchange, solvent extraction, selective precipitation andelectrowinning.

Only the basics of the mineral processing system 2 have been illustratedin FIG. 1, and it should be understood that a variety of specificprocessing actions may be performed in any of the steps depending uponthe particular application. For instance, the mineral material feedsupply system 6 will typically include comminution of a mineral material(e.g., crushing and/or grinding) before being slurried with anappropriate liquid (e.g., aqueous liquid). Furthermore, the supplysystem 6 could include a flotation operation to prepare a sulfideconcentrate to be used as or as part of the mineral material feed to thereactor 26. Also for instance, the metal recovery system 82 may include,without limitation, one or more of reducing the temperature of thedischarge from the reactor 26, conditioning of the discharge (e.g., pHadjustment), and/or one or more liquid/solid separations.

The mineral material feed to the reactor 26 will typically be inparticulate form of any convenient size for processing through thereactor 26. For many applications, the mineral material feed will besized so that at least about 80% of the mineral material feed is smallerthan about 200 mesh (i.e., P80 size of 200 mesh or smaller). As fed tothe reactor 26, the mineral material feed will be in a slurry withwater. The feed slurry, may have any solids content that is convenientfor processing through the reactor 26. Typically the slurry will have asolids content of at least about 20 weight percent solids, and moreoften from about 35 weight percent to about 55 weight percent solids.Various features are utilized in relation to the reactor 26 to enhanceone or more aspects of the chemical processing operation occurring inthe reactor 26, as noted, and is discussed below in more detail. Thetemperature and pressure conditions in the reactor 26 will depend uponthe mineral material that is being processed and the specific operationbeing performed. In the case of pressure oxidation and pressure leachingoperations, the reactor 26 will be operated at high pressures,frequently in excess of 100 psig (689 kPa), and at a high temperature,frequently in excess of 100° C. Unless otherwise specified, all listedpressures are gauge pressure, and not absolute pressures. For example,when pressure oxidizing a sulfide gold ore or concentrate, thetemperature will typically be higher than about 160° C., and more oftenin a range of from about 180° C. to about 240° C. Furthermore, forpressure oxidation operations, Oxygen gas will typically be fed to thereactor 26 at an over pressure (i.e., over and above vapor pressureexerted by the aqueous liquid in the reactor 26) of at least about 10psi (69 kPa) and more often in a range of from about 25 psi (172 kPa) toabout 100 psi (689 kPa). The metal recovery system 82 will typicallyentail a cooling system to reduce the reactor discharge slurry to asuitably low temperature for metal recovery operations, which is oftento a temperature of lower than about 50° C.

Reference is now made to FIG. 2, which illustrates the details of oneembodiment of the reactor 26 that may be used in the mineral processingsystem 2 of FIG. 1 when a pressure oxidation operation is to beperformed in the reactor 26. Although the reactor 26 as described withreference to FIG. 2 is specifically designed for pressure oxidation,features described concerning agitation and feeding materials into thereactor 26 in relation to one or more agitators disposed in the reactor26 are equally applicable to pressure leaching operations and to othermineral processing operations involving mixing of components.

The reactor 26 as shown in FIG. 2 is a four-stage reactor and generallyincludes an appropriately configured/sealed pressure vessel 30 having abottom 40 and a vertically spaced top 36. The interior of the pressurevessel 30 includes a plurality of longitudinally-spaced dividers 38which extend upwardly from the bottom 40 and which separate the interiorof the pressure vessel 30 into stages or compartments 34. “Longitudinal”in this context means at least generally in the direction of slurry flowthrough the pressure vessel 30, and which longitudinal direction isrepresented by the arrow “A” in FIG. 2. The noted dividers 38 are spacedfrom the top 36 to provide an opening above the top of the dividers 38for flow of slurry between adjacent compartments 34, in the direction ofthe arrow “A”, progressing from the first compartment 34 a to the secondcompartment 34 b, then to the third compartment 34 c and finally to thefourth compartment 34 d.

An agitator 62 is disposed in each of the compartments 34 a-d of thereactor 26. Only a schematic representation of the agitator 62 isprovided in FIG. 2. Details regarding a number of preferredconfigurations for the agitator 62, providing an enhanced pumpingagitation function and enhancing efficiency of oxygen utilization, areaddressed below in relation to FIGS. 3-7. Each agitator 62 generallyincludes an agitating member 68 and an agitator drive shaft 66 which isappropriately fixedly interconnected therewith. Rotation of theagitating member 68 of each agitator 62 is effected by appropriatelyinterconnecting each the agitator drive shaft 66 with an appropriateagitator drive assembly (not shown). Any way of rotating each of theagitators 62 may be utilized/implemented by the agitator drive assembly.For instance, each of the agitators 62 could be rotated by a commonsource, or each agitator 62 could be rotated by its own source.Typically, each agitator 62 is independently driven by a separate motorassociated with each agitator 62. Moreover, one or more of the agitators62 may be rotated at the same or different speeds. In one embodiment,each of the agitators 62 are rotated at substantially the samerotational velocity.

There are a number of different flows which are directed into thepressure vessel 30. One of these flows is a slurry including the mineralmaterial feed 43 provided by the mineral 33 material feed supply slurrysystem 6. Instead of only providing a single flow of the mineralmaterial slurry to the reactor 26 in the manner of the known prior art,the mineral material feed supply system 6, as shown in FIG. 2,simultaneously directs a portion of the mineral material feed into eachof the first compartment 34 a and the second compartment 34 b. In thisregard, the mineral material feed supply system 6 includes a firstslurry supply line 14 a and a second slurry supply line 14 b, which aredisposed in the first compartment 34 a and the second compartment 34 b,respectively. How the mineral material feed is actually directed fromthe mineral material feed supply system 6 to each of the first slurrysupply line 14 a and the second slurry supply line 14 b is not ofparticular importance. In this regard, the mineral material slurrysupply system 6 contemplates: 1) directing a single feed inlet conduitfrom the mineral material feed supply system 6 through a wall of thepressure vessel 30 for fluidly interconnected with each of the firstslurry supply line 14 a and the second slurry supply line 14 b; 2) usinga single pump to direct a flow of the mineral material slurry that issplit between the first slurry supply line 14 a and the second slurrysupply line 14 b; 3) using appropriate valving to allow for metering ofand/or otherwise controlling the flow/flow rate through each of thefirst slurry supply line 14 a and the second slurry supply line 14 b; 4)and having the first slurry supply line 14 a being in independent fluidinterconnection with the mineral material feed supply system 6 and withthe flow being directed therethrough by a first pump or the like, andhaving the second slurry supply line 14 b being in independent fluidcommunication with the mineral material feed supply system 6 and withthe flow being directed therethrough by a second pump or the like, suchthat there would be two penetrations of the pressure vessel 30 tointroduce the mineral material feed (e.g., two slurry feed inletconduits passing through the wall of the pressure vessel 30). In oneembodiment, a single slurry feed inlet conduit passes through a wall ofthe pressure vessel 30, extends at least generally along the bottom 40of the pressure vessel 30 within the first compartment 34 a and at leastgenerally in the direction of the arrow “A”, extends through the firstdivider 38 a, and thereafter extends at least generally along the bottom40 of the pressure vessel 30 within the second compartment 34 b. Each ofthe first slurry supply line 14 a and the second slurry supply line 14 b“tap into,” or are fluidly interconnected with, this single slurry feedinlet conduit in this instance.

Regarding the relative magnitudes of flow rates of mineral material feedthrough each of the slurry supply lines 14 a and 14 b, typically fromabout 10 percent to about 90 percent of the feed is introduced into thefirst compartment 34 a and the remaining into the second compartment 34b. In a preferred embodiment, at least about 25 weight percent, and morepreferably at least about 50 weight percent, of the total mineralmaterial feed is introduced into the first compartment 34 a. Forexample, in one embodiment, about 55 weight percent of the total mineralmaterial feed is introduced into the first compartment 34 a and about 45weight percent of the total mineral material feed is introduced into thesecond compartment 34 b. It should be appreciated that a portion of themineral material feed could be introduced into compartments 34 c and/or34 d, but such an operation is generally not preferred.

Introducing a separate flow of mineral material feed into each of thefirst compartment 34 a and the second compartment 34 b enhances one ormore aspects of the pressure oxidation that occurs within the reactor26. Other aspects in relation to introduction of the mineral materialfeed into the reactor 26 further enhance one or more aspects of thepresent invention. FIG. 2 clearly illustrates that the slurry supplylines 14 a and 14 b each direct a separate flow of the mineral materialslurry into the reactor 26 in an at least generally upward directionwith the flow being introduced into the reactor 26 at an upward anglerelative to horizontal so that the flow is at least generally toward thetop 36 of the pressure vessel 30, as illustrated by each arrow “B”. Theupwardly directed flow of mineral material feed is effected in thereactor of FIG. 2 by having a discharge end portion 18 a and 18 b ofeach of the slurry supply lines 14 a and 14 b extend at least generallyaway from the bottom 40 of the pressure vessel 30 at an upward anglerelative to horizontal, preferably at an acute angle relative tohorizontal. The discharge end portion 18 of each slurry supply line 14is typically disposed at an upward angle typically in a range of fromabout 5 degrees and about 90 degrees relative to horizontal, with anupward angle of at least about 30 degrees relative to horizontal beingpreferred, and with an upward angle of from about 30 degrees to about 60degrees being even more preferred. In one preferred embodiment, theupward angle of the direction of the discharge end 18 is at an upwardangle of about 45 degrees relative to horizontal. Not only is thedischarge end portion 18 of each slurry supply line 14 and correspondingflow of mineral material feed directed at least generally upward, butthe flows of mineral material feed are at least generally upward in adirection toward the corresponding agitator member 68 (i.e., member 68 acorresponding with supply line 14 a in compartment 34 a, etc.).Preferably the discharge end 18 of each slurry supply line 14, and alsothe corresponding flow of mineral material feed, is at least generallydirected at a fluid intake of the corresponding agitator 62.

Another flow introduced into the reactor 26 is oxygen gas from an oxygensupply system 50 fluidly interconnected with the interior of thepressure vessel 30 to introduce oxygen gas into the pressure vessel 30at one or more location, and more preferably at a plurality of differentlocations. In the illustrated embodiment shown in FIG. 2 there is anoxygen supply line 58 disposed in each of the compartments 34 a-d witheach oxygen supply line 58 being appropriately fluidly interconnectedwith the oxygen supply system 50.

Oxygen is thereby preferably directed into the slurry within eachcompartment 34 of the reactor 26. The oxygen supply system 50contemplates: 1) directing a single oxygen feed inlet conduit from theoxygen supply system 50 through a wall of the pressure vessel 30 forfluid interconnection with each of the oxygen supply lines 58; 2) usinga single pressure

source to direct a flow which is split between the oxygen supply lines58; 3) using appropriate valving to allow for metering of and/orotherwise controlling the flow/flow rate through each of the oxygensupply lines 58; and 4) having each of the oxygen supply lines 58 beingindependently fluidly interconnected with their own oxygen source andwhich would collectively define an oxygen supply, such that there wouldpossibly be 4 penetrations of the pressure vessel 30 by the oxygensupply system 50 (e.g., four oxygen feed inlet conduits which would passthrough the pressure vessel 30). In one embodiment, a single oxygen feedinlet conduit passes through a wall of the pressure vessel 30, extendsat least generally along the bottom 40 of the pressure vessel 30 withinthe each of the compartments 34 and at least interconnected therewith.

Although it is possible to feed air to the reactor to introduce theoxygen gas into the reactor, it is preferred that the oxygen gas isintroduced in a gas stream substantially enriched in oxygen gas relativeto air. The oxygen supply system 50 may include compressed oxygen gasstorage to supply the oxygen gas, or, preferably, an oxygen plant thatproduces an oxygen-enriched gas stream from air. The oxygen plant mayemploy any technique for producing the oxygen-enriched gas stream, suchas for example membrane or cryogenic separation.

Regarding the relative magnitudes of flow rates of oxygen gas througheach of the oxygen supply lines 58, typically a larger portion of totaloxygen gas introduced into the reactor 26 is introduced into thosecompartments 34 into which mineral material feed is also introduced(compartments 34 a and 34 b in the embodiment shown in FIG. 2).Preferably, the allocation of oxygen gas feed between the compartmentsthat receive mineral material feed (i.e., compartments 34 a and 34 b inFIG. 2) is in proportion to the allocation of total mineral materialfeed between the same compartments. Therefore, for example, when the twocompartments 34 a and 34 b each receive equal quantities of mineralmaterial feed, they also preferably each receive equal quantities ofoxygen gas. For example, when 50 percent of total mineral material feedis introduced into each of the first and second compartments 34 a and 34b, compartments 34 a and 34 b might each be allocated an equal oxygengas flow of about 46 percent of the total oxygen gas, the thirdcompartment 34 c might be allocated about 5 percent of the total oxygengas, and the fourth compartment 34 d might be allocated only about 3percent of the total oxygen gas. Splitting total mineral material feedbetween compartments 34 a and 34 b, and adjusting oxygen gas input intocompartments 34 a and 34 b accordingly, significantly promotesattainment of efficient oxygen gas utilization in the reactor 26.

There are also a number of important features shown in FIG. 2representing refinements in relation to how oxygen gas may be introducedinto the reactor 26. One such feature is that the flow of oxygen gas isintroduced into each the compartments 34 in an at least generally upwarddirection, meaning that, the flow is introduced into the reactor 26 atan upward angle relative to horizontal so that the flow is at leastsomewhat vertically inclined. As shown in FIG. 2, the oxygen gas flow isdirected substantially vertically upward, as illustrated by the arrows“C” in FIG. 2, which is the most preferred orientation for oxygen gasflow. The upwardly directed flow is effected in the reactor of FIG. 2 byhaving discharge portions of oxygen supply lines 58 extend at leastgenerally away from the bottom 40 of the pressure vessel 30 at an upwardangle relative to horizontal. The discharge end portions of the oxygensupply lines 58, and therefor also the direction of flow of the oxygengas in the reactor 26, is typically disposed at an upward angle relativeto horizontal of from about 5 degrees to about 90 degrees, preferablyfrom about 30 degrees to about 90 degrees, more preferably from about 45degrees to about 90 degrees, and most preferably at about 90 degrees (sothat the flow of oxygen gas is directly vertically upward, as shown inFIG. 2). Another refinement shown in FIG. 2 is that the flow of oxygengas out of each of the oxygen supply lines 58 is directed at leastgenerally upward toward the corresponding agitator member 68 (i.e., theagitator member 68 a corresponding with oxygen supply line 58 a incompartment 34 a, etc.). More preferably, the discharge end portion ofeach oxygen supply line 58, and also the direction of oxygen gas flow,are axially aligned with the center of the corresponding agitator 62,which typically also corresponds with the rotational axis of thecorresponding agitator 62, as defined by the agitator drive shaft 66.

Maintaining certain relative relationships involving the oxygen supplylines 58 further promote efficient oxygen utilization by the reactor 26.Disposing the end of each oxygen supply line 58 at least relativelyclose to its corresponding agitator 62 enhances oxygen uptake by theagitator to promote effective dispersion of the oxygen in the slurry. Inone embodiment, the end of each oxygen supply line 58 is separated fromits corresponding agitator 62 by a distance of no larger than about 12inches, and preferably by no larger than about 6 inches. Moreover, therelative positioning of discharge end portions of the slurry supplylines 14 and oxygen supply lines 58 is important to enhancedperformance. Preferably, each slurry supply line 14 and thecorresponding oxygen supply line 58 are oriented such that thecorresponding flows of mineral material feed and oxygen gas in acompartment 34 are directed along lines that intersect in the vicinityof the corresponding agitator 62, and more preferably in close proximityto a fluid intake to the corresponding agitator 62. This intersectionwill typically be at or below a fluid intake located on the verticalbottom of the agitator 68. Intersection of corresponding flows ofmineral material feed and oxygen gas in close proximity to a fluidintake of the corresponding agitator 62 significantly promotesdispersion of oxygen gas by the agitator 62 and thereby also promotesefficient utilization of oxygen during pressure oxidation. Furthermore,in one embodiment, the discharge end of each slurry supply line 14 isdisposed at about the same vertical elevation as the discharge end ofthe corresponding compartment oxygen supply line 58.

In addition to efficient use of oxygen gas, operation of the reactor 26as shown in FIG. 2 also provides advantages in relation to thermalefficiency, which can permit processing of higher throughputs, aspreviously discussed. In many cases, it is necessary to add supplementalheat to at least the first compartment 34 a from an external source toachieve the desired reaction temperature. This is especially the casewhen processing a mineral material feed containing a low sulfide sulfurcontent. This external heat may be supplied from a steam supply system42, as shown in FIG. 2, that is fluidly interconnected with the interiorof the pressure vessel 30 in an appropriate manner to permit theintroduction of stream into the reactor at one or more locations.Furthermore, just as it is often necessary to add heat to one or moreupstream compartment 34 (e.g., one or more of compartments 34 a and 34b), so also it is often necessary to cool one or more downstreamcompartment 34 (e.g., one or more of compartments 34 c and 34 d), toprevent the temperature in such downstream compartment(s) from becomingexcessively high. This may be accomplished by the addition of water toone or more of the downstream compartments 34 from a cooling watersupply system 46, as shown in FIG. 2, fluidly interconnected with theinterior of the pressure vessel 30 in a appropriate manner to permit theintroduction of water into the reactor 26 at one or more locations toreduce the temperature during pressure oxidation. Furthermore, the moresteam that is added into one or more upstream compartments 34 of thereactor, the more water will be required for cooling of one or moredownstream compartments 34. With the present invention, steam additionsfrom the steam supply system 42 can typically be reduced, and so alsocan water additions from the cooling water supply system 46 be reduced,providing further advantages with the present invention. As notedpreviously, by splitting total mineral material feed between the firstand second compartments 34 a and 34 b, lower steam and water additionsare typically achievable.

One benefit from reducing the additions of steam and/or water is thatthe operational cost of generating the steam for heating and/orproviding the water for cooling is reduced. An often more importantbenefit, however, is that lower stream and/or water additions permit ahigher density slurry (i.e., slurry containing higher solids content) tobe processed through the reactor 26, thereby increasing the quantity perunit time of mineral material feed that may be pressure oxidized. Thisis because steam and water additions dilute the density of the slurry inthe reactor 26, which has the effect of reducing the rate at which feedslurry can be introduced into the reactor 26.

In the reactor 26 shown in FIG. 2, one agitator 62 is disposed in eachcompartment 34 to agitate the contents of the reactor 26. Morespecifically, the agitator 62 shears oxygen gas bubbles to dispense theoxygen gas throughout the slurry in the reactor 26 to promote rapiddissolution of oxygen from the oxygen gas into the aqueous liquid phaseof the slurry. It has been found with the present invention thatincreased oxygen utilization can often be realized by using an agitator62 that cycles slurry within the reactor with a pumping action, topromote better gas dispersion within the reactor 26. An agitatoroperating with such a pumping action may be referred to as an agitatorpump. Details regarding one embodiment of such an agitator isillustrated in FIGS. 3-5, which show one embodiment of an agitator pump90 that could be used in place of one or more of the agitators 62generally depicted in FIG. 2, and which will be described as if soinstalled in the reactor 26 in the place of one or more of the agitators62.

With reference to FIGS. 2-5, the agitator pump 90 generally includes anupper partition 98 and a lower partition 106, which is disposed invertically spaced relation to the upper partition 98. In the illustratedembodiment, the upper partition 98 and lower partition 106 are alsodisposed at least generally parallel to each other, which is thepreferred configuration/orientation. Each of the upper partition 98 andlower partition 106 are in the form of a single-piece circular plate inthe illustrated embodiment, with the upper partition 106 being of alarger diameter than the lower partition 106. Other configurations,assemblies and relative sizings may be utilized for one or both of theupper partition 98 and lower partition 106, so long as the upperpartition and the lower partition form opposing barriers to define apump cavity, as discussed below.

The space between the upper partition 98 and lower partition 106 definesa pump cavity 118. Access for drawing fluid into this pump cavity 118 isprovided through a pump inlet aperture 110 which extends entirelythrough the lower partition 106. The pump inlet aperture 110 therebyprojects at least generally toward the bottom 40 of the reactor 26.Preferably the center of the pump inlet aperture 110 is colinear withthe rotational axis 96 of the agitator pump 90 as defined by itsagitator pump drive shaft 94.

Generation of a pumping action by the agitator pump 90 is effected byrotating the pump drive shaft 94 to cause rotation of a plurality ofradially-spaced vanes 114 through slurry contained within the reactor 26during pressure oxidation. Preferably the vanes 114 are regularlyspaced, and preferably there are at least about 2 of such vanes 114, andmore preferably at least 4 (8 of the vanes 114 are shown in theillustrated embodiment). Typically the entirety of these vanes 114 willbe totally submerged within slurry in the reactor 26 during pressureoxidation, and rotation of the agitator pump 90 about the rotationalaxis 96 causes the vanes 114 to propel slurry within the relevantcompartment 34 radially outwardly relative to the rotational axis 96.The propulsion of slurry radially outwardly by the vanes 114 causesdevelopment of a lower pressure region, creating a fluid suction, withinthe pump cavity 118, which draws slurry and oxygen gas into the pumpcavity 118 via the pump inlet aperture 110. Therefore, rotation of thevanes 114 about the rotational axis 96 effects a pumping action in whichslurry is continually drawn into the pump cavity 118 through the pumpinlet aperture 110 and expelled radially outward from the cavity,thereby agitating and mixing the contents of the reactor 26. Oneagitator structure, as shown in FIGS. 3-5, for effecting the pumpingaction is by fixedly attaching the drive shaft 94 to the upper partition98, and further by fixedly attaching each of the plurality of vanes 114to both the upper partition 98 and the lower partition 106. Other waysof assembling the agitator pump 90 could, however, be utilized insteadas long as the pumping action is achieved.

Both the mineral material slurry and the oxygen gas enter the pumpcavity 118 of the agitator pump 90 through the pump inlet aperture 110formed through the lower partition 106. In the embodiment illustrated inFIGS. 3-5, the agitator pump includes a pump inlet conduit 122interfacing with the lower partition 106 in alignment with the pumpinlet aperture 110. This pump inlet conduit 122 is appropriatelyinterconnected with the lower partition 106 and, when the agitator pump90 is installed in the reactor 26, extends a least generally in adownward direction toward the bottom 40 of the pressure vessel 30. Inthe illustrated embodiment, the pump inlet conduit 122 is disposed invertical relation and is colinear with the agitator pump drive shaft 94.Moreover, the pump inlet conduit 122 of each agitator pump 90 ispreferably colinear with its corresponding oxygen supply line 58 (asshown in FIG. 2) within the reactor 26 (i.e., such that their centersare aligned). In the illustrated embodiment of the agitator pump 90, theopen lower end 123 of the pump inlet conduit 122 serves as a fluidintake to the agitator pump 90, such that when in operation, slurrywithin the reactor 26 initially enters into the agitator pump 90 throughthe open lower end 123 of the pump inlet conduit 122 to be directedthrough the pump inlet aperture 110 into the pump cavity 118. Theagitator pump 90 could be constructed and used without the pump inletconduit 122. In that case, slurry would initially enter the agitatorpump 90 directly through the pump inlet aperture 110 (rather thanindirectly through the pump inlet conduit 122), and the pump inletaperture 110 would serve as a fluid intake to the agitator pump 90. Thedesign of the agitator pump 90 could obviously be modified to include avariety of configurations for a fluid intake. In a preferred design,however, the agitator used with the present invention to provide thepumping action has a fluid intake that opens toward the bottom 40 of thereactor 26.

Use of the pump inlet conduit 22, is, however, preferred. The pump inletconduit 122 constrains the flow of slurry, focuses the flow to agenerally central location of the pump cavity 118, and/or promotescapture of oxygen gas for effective delivery to the pump cavity 118.Moreover, the pump inlet conduit 122 distances the location of fluidintake into the agitator pump 90 from fluid expulsion from the agitatorpump 90, and thereby tends to reduce the potential for premature cyclingof slurry through the pump agitator 90.

In one embodiment, it is preferred to position the upper end of eachcompartment oxygen supply line 58 relatively close to the open lower end123 of the pump inlet conduit 122. In one embodiment, there is about a 2inch (5 cm) separation between the end of each compartment oxygen supplyline 58 and its corresponding pump inlet conduit 122. Preferably,however, the spacing between a fluid intake of the agitator pump 90 anddischarge end of a corresponding oxygen supply line 38 is no larger thanabout 12 inches (30 cm), and more preferably is no larger than about 6inches (15 cm). Furthermore, it is preferred that the discharge end ofthe oxygen supply line 58 be located directly below the correspondingfluid intake, so that the flow of oxygen gas is directed substantiallyvertically upward toward the fluid intake.

Various orientations and/or configurations may be utilized for the vanes114 of the agitator pump 90. FIGS. 3-5 illustrate an embodiment in whichthe vanes 114 have the following characteristics: 1) the vanes 114extend in a radially outwardly direction in relation to the rotationalaxis 96 of the agitator pump 90; 2) the vanes 114 each initiate at thepump inlet aperture 110 and extend radially outwardly therefrom (i.e.,the radially inward most portion of each of the vanes 114 terminates atthe perimeter of the pump inlet aperture 110); 3) the vanes 114 eachextend between the upper partition 98 and lower partition 106 from theupper partition 98 entirely down to the lower partition 106; 4) thevanes 114 each extend radially outwardly beyond a perimeter 102 of theupper partition 98, and also beyond a perimeter 108 of the lowerpartition 106; 5) the vanes 114 each extend vertically downward at theperimeter 108 of the lower partition 106 to a location vertically lowerthan the lower partition 106; 6) the vanes 114 each extend verticallyupward at the perimeter 102 of the upper partition 98 to a locationvertically about the upper partition 98; and 7) a portion of each of thevanes 114 are disposed on top of and interface with a surface of theupper 98 that is opposite the surface defining the upper extreme of thepump cavity 118 (e.g., an outer portion of the upper partition 98 isdisposed within a notch formed in the vanes 114).

A variation of the embodiment of the agitator pump shown in FIGS. 3-5 ispresented in FIGS. 6-7 and 12. Components from the embodiment of FIGS.3-5 which are utilized by the embodiment of FIGS. 6-7 are identified bythe same reference numerals. A single prime designation is utilized toidentify that there are, however, distinctions between the twoembodiments. The primary distinction between the agitator pump 90′ ofFIGS. 6-7 and the agitator pump 90 of FIGS. 3-5 is in relation to theconfiguration/construction/orientation of the vanes 150 (FIGS. 6-7)compared to the vanes 114 (FIGS. 3-5). Initially, the vanes 150 utilizea two-part construction, whereas the vanes 114 are illustrated in theform of a unitary construction. In this regard, the vanes 150 of theagitator pump 90′ include a fin 154 and a blade 158 disposed in abuttingrelation to the fin 154 and extending radially outwardly from the fin154. A portion of each fin 154 extends over a portion of the pump inletaperture 110, as illustrated in FIG. 7. That is, a radially inwardmostportion of the fin 154 is disposed inwardly from a perimeter of the pumpinlet aperture 110. In the case of the agitator pump 90′, the vanes 150do not extend radially outwardly from the rotational axis 96, butinstead are slightly offset therefrom. This is shown in FIG. 12, whereit is seen that the vanes 150 do not converge at the rotational axis 96,but are slightly offset from the rotational axis 96. Moreover, in theembodiment of the agitator pump 90′ shown in FIG. 12, the fins 154 ofthe vanes 150 are offset from the rotational axis 96 in a manner to forma geometric pattern about the rotational axis 96 overlying the inletaperture 110. The agitator pump 90′, as shown in FIG. 12, wouldordinarily be rotated in a clockwise direction during operation.

The vanes 150 of FIGS. 6-7 also utilize a different configuration thanthat of the vanes 114 from FIGS. 3-5. FIGS. 6-7 illustrate that thevanes 150 have the following characteristics: 1) both the fins 154 andthe blades 158 (portion 170) extend from the upper partition 98 entirelydown to the lower partition 106; 2) the fins 154 do not extend beyondthe perimeter 102 of the upper partition 98 or beyond the perimeter 108of the lower partition 106; 3) the blades 158 extend beyond theperimeter 102 of the upper partition 98 and also beyond the perimeter108 of the lower partition 106; 4) the blades 158 extend verticallydownward at the perimeter 108 of the lower partition 106 (i.e., thelower extreme of portion 170 is disposed at the same elevation as thatsurface of the lower partition 106 which defines the lower extreme ofthe pump cavity 118); 5) a portion 168 of the blades 158 extendsradially outwardly from the perimeter 102 of the upper partition 98; 6)a portion 162 of the blades 158 is disposed at a higher elevation thanthe upper partition 98; and 7) the blades 158 are disposed on top of andinterface with a surface of the upper partition 98 opposite that whichdefines the pump cavity 118, including a portion 166 which is used tointerconnect the blade 158 with the upper partition 98.

One way of constructing the agitator pump 90′ is as follows: 1) theagitator pump drive shaft 94 is bolted onto the upper partition 98 withan appropriate flange (not shown); 2) the plurality of fins 154 arewelded to the upper partition 98 in the desired position (i.e. the upperpartition 98 and the fins 154 are metal in one embodiment); 3) the lowerpartition 106 is disposed in the desired position and each of the fins154 are welded to the lower partition 106 (i.e., the lower partition 106is metal in one embodiment); and 4) the blades 158 are disposed inproper alignment and are detachably interconnected with the upperpartition 98 by one or more mechanical fasteners 174. In one embodimentthe blades 158 are of a unitary or integral construction (i.e., suchthat there is no mechanical joint of any kind), and are formed frommaterials such as ceramic or titanium. As such, the blades 158 can bereplaced as needed.

Although the description in reference to FIGS. 1-7 and 12 provided abovehas been primarily in reference to a specific type of reactor used forpressure oxidation operations, the features described are applicablealso to other chemical processing situations. For example, the disclosedagitator embodiments can be incorporated into any reactor having aninterior reactor volume that is susceptible to agitation or mixing ofthe type provided by the agitator of the present invention. Also, thediscussion above in relation to the manner of introducing oxygen gas andmineral material feed into the reactor for pressure oxidation operationsapplies also to the introduction of any components into other reactorsystems in combination with the agitation of the present invention. Forexample, one or more flows of feed containing components to be mixedcould be fed in any chemical processing operation into the relevantreactor in an upwardly directed flow toward the fluid intake of theagitator. The locational relationships between the introduction of feedsand the agitator are easily translatable between different chemicalprocessing operations. This is so even though any particular chemicalprocessing operation may have more or fewer than the two feed streams asdiscussed with respect to FIG. 2. For example, during pressure leachingoperations, it would be preferred to direct the feed of mineral materialin an upward flow toward the fluid intake of the agitator, even thoughthere is no flow of oxygen gas being introduced into the reactor.Likewise, other chemical processing operations may have three or morefeed streams that could be directed at the fluid intake of the agitator,if desired, to promote efficient mixing of the feed components throughthe agitator according to the present invention. Furthermore, when usinga multi-stage reactor, splitting of feed streams between compartments,in a manner as discussed above for pressure oxidation, can beadvantageously applied to other reactor systems when using a multi-stagereactor, such as for example when the situation involves an exothermicprocess or some other attribute conducive to splitting feed betweencompartments.

In a general sense, the aspects of the present invention involvingagitation, and also refinements thereto concerning introduction of feedstreams in relation to the agitation, are applicable to any chemicalprocessing situation when it is desirable to mix two or more componentsin a contained volume of a flowable medium. As used herein, a flowablemedium refers to a medium that has properties of flowability sufficientto be cycled through the agitator pump useful with the presentinvention. Such flowability is typically provided by the presence of aliquid in the medium at least to the extent that the medium exhibitsfluid properties of flow, such as is the case with the slurriescontaining particulate mineral materials that may be processed duringpressure oxidation and pressure leaching operations. Therefore, forexample, the flowable medium will typically include at least one liquidphase, but may include two or more liquid phases, which could be in theform of an emulsion or otherwise. Moreover, the flowable medium mayinclude one or more gaseous phases, such as is the case with the oxygengas during pressure oxidation operations. Also, as noted, the flowablemedium can include one or more particulate solid phases, such as in theslurries processed during pressure oxidation and pressure leaching.

One mixing situation for application of the present invention involvesmaintaining a multi-component, and typically multi-phase, flowablemedium in a well mixed state, which may be referred to ashomogenization. In this situation, the agitation is used simply toprevent phase separation, such as preventing settling of solidparticulates in a slurry medium. One aspect of the agitation of theinvention as used in pressure oxidation and pressure leaching operationsis that the agitation maintains a homogenized mixture of the solids andliquid in the reactor during processing.

Another mixing situation for application of the present inventioninvolves dispersing material from a feed stream introduced into a volumeof flowable medium throughout the volume. In this situation, theagitation is preferably combined with introduction of the feed materialin a flow directed at a fluid intake of an agitator pump. One aspect ofthe agitation of the invention as used in pressure oxidation andpressure leaching is that fresh mineral material feed introduced intothe reactor is dispersed throughout the reactor by the agitation. In thecase of pressure oxidation, the agitation also effects dispersion of theoxygen gas in the flowable medium. It should be noted that the materialto be dispersed may or may not be a reactant in the system. In the caseof pressure oxidation, for example, the oxygen gas is a reactant. Suchmay not be the case for other systems. For example, in wastewaterprocessing operations, the agitation of the present invention could beused to aerate water, even though the aeration gas does not contain areactant.

Yet another mixing situation for application of the present inventioninvolves mixing two or more different feed streams with each other andalso with a contained volume of flowable medium. For example, in thecase of pressure oxidation, flows of both the mineral material feed andthe oxygen gas feed may be directed toward the fluid intake to anagitator pump, effecting both intimate mixing of the oxygen gas with themineral material feed and dispersion of both the oxygen gas and themineral material feed throughout the reactor volume.

The agitation of the present invention operates most effectively whenprocessing flowable mediums of a high viscosity, so long as theviscosity of the medium is at least low enough that the medium is infact practically flowable through the agitator. Slurries, such as thoseencountered during pressure oxidation and pressure leaching operations,typically exhibit high viscosities. It has traditionally beenparticularly difficult to obtain good mixing of such high viscositymediums. In that regard, it was found during pressure oxidation ofcertain refractory sulfide gold ores that as the viscosity of the slurrybecame higher, it became more difficult to achieve good sulfideoxidation, limiting the density of slurries that could be effectivelyprocessed to those of around 35-40 weight percent solids or lower. Withthe present invention, however, slurry densities as high as 55 weightpercent, and possibly higher, may be effectively pressure oxidized. Ingeneral, the agitation of the present invention is well suited formixing/agitating a flowable medium having a viscosity greater than about10 centipoise, preferably greater than about 100 centipoise and morepreferably greater than about 1000 centipoise.

As discussed above, one specific example of a chemical processingoperation for application of one or more aspects of the presentinvention is pressure oxidation. The pressure oxidation may involveprocessing any metal-containing sulfide mineral material feed.Non-limiting examples of sulfide minerals that may be processed arethose including one or more of copper, nickel, zinc, lead, cobalt,vanadium, tungsten, molybdenum, silver and iron. When pressure oxidizingiron sulfides, the object is often to recover gold or some otherprecious metal contained within the iron sulfide mineral. In the case ofmost of these metals, such as for example copper, nickel, zinc and lead,the metal of interest will ordinarily dissolve into the liquid phaseduring the pressure oxidation operation. As noted previously, gold willtypically remain with solid residue from the pressure oxidationoperation.

Another specific example of a chemical processing operation forapplication of one or more aspects of the present invention is pressureleaching. Pressure leaching can be performed on any mineral materialcontaining a metal that is directly leachable from the mineral material.Mineral materials processed by pressure leaching are most often oxidizedores or concentrates made from flotation of such ores. Non-limitingexamples of metals that may be processed by pressure leaching includecopper, nickel, zinc, lead, cobalt, gold, silver, platinum, palladium,vanadium, uranium, tungsten, molybdenum, manganese, and aluminum, to theextent those metals are contained within mineral materials that aredirectly leachable, such as in many oxide ores or concentrates thereof.

With respect to pressure oxidation and pressure leaching, processing ofmineral material feed is primarily contemplated, as discussed above. Thescope of the invention is not, however, so limited. Pressure oxidationcould be performed on any metal sulfide material in a form that can beslurried for processing, and pressure leaching could be performed on anyleachable metal containing material in a form that can be slurried forprocessing. As one example, copper, gold, silver, platinum, palladiumand/or other conductive metals could be pressure leached from groundcircuit boards or other electrical components containing the metal(s).

Yet another specific example of a chemical processing application forone or more aspects of the present invention is water treatment, andspecifically for aeration of water, or aeration of sludge producedduring wastewater treatment operations.

Still another specific example of a chemical processing application forone or more aspects of the present invention is paper industry formixing whiteners, such as peroxides, into paper pulp slurries.

A number of examples are provided to further illustrate one or moreaspects of the present invention and/or advantages associated with oneor more such aspects.

Data from the examples is presented tabularly in the Tables 1-4, asreferenced in the examples. Because the same format is used in each ofthese Tables, a brief discussion of that format is provided at thispoint. In Tables 1-3, Column 1 lists different ranges of sulfide sulfurcontent in mineral material feed for different processing runs, and isexpressed as weight percent sulfide sulfur in the mineral material feed.The “+” sign for the highest range of sulfide sulfur content means thatthe sulfide sulfur content was equal to or greater than the notedamount, whereas the “−” sign for the lowest range means that the sulfidesulfur content was equal to or smaller than the noted amount. Column 2shows the average flow rate of mineral material feed in tons of mineralmaterial per 12-hour operating shift fed into the reactor for variousprocessing runs. Column 3 shows the average weight percent of sulfidesulfur in the mineral material for various processing runs. Column 4shows the average quantity in tons per 12-hour operating shift ofsulfide sulfur processed for various processing runs. Column 5 shows theaverage weight percent of sulfide sulfur in solid residue dischargedfrom the reactor for various processing runs. Column 6 shows the averagequantity of oxygen gas in thousands of pounds per 12-hour operatingshift fed to the reactor for various processing runs. Column 7 shows theaverage concentration of free acid in liquid discharged from thereactor, in grams of acid per liter of liquid, for various processingruns. Column 8 shows the average gold recovery by cyanide leaching ofthe reactor discharge as a percentage of gold originally in the mineralmaterial feed for various processing runs. Column 9 shows the averageextent of sulfide sulfur oxidation occurring in the reactor, expressedas a percentage of sulfide sulfur originally in the mineral materialfeed, for various processing runs. Column 10 shows the average ratio ofthe pounds of oxygen gas fed to the reactor per pounds of sulfide sulfuroxidized in the reactor for various processing runs. Column 11 shows theaverage oxygen utilization efficiency expressed as a percentage of theoxygen gas fed to the reactor that is consumed to oxidize sulfide sulfurin the reactor for various processing runs, calculated based onstoichiometric oxygen requirements to oxidize that quantity of sulfidesulfur actually oxidized. In table 4, Columns 1-10 provide aconsolidated summary of the same data provided in Columns, 2-11 ofTables 1-3.

EXAMPLE 1

A slurry of refractory sulfide gold ore and/or concentrate from the LoneTree Mine, of Newmont Mining Corporation, in Nevada, U.S.A. isintroduced in a vertically downward direction into the lower portion ofthe first compartment of a four-stage autoclave, while oxygen gas isintroduced horizontally into the lower portion of each compartment, asshown schematically in FIG. 9. The sulfide gold ore/concentrate is inparticulate form having a P80 size of about 200 mesh. An agitator isdisposed in each stage of the autoclave. Each of the agitators in thefirst two compartments has a design as shown in FIG. 8. FIG. 8 shows anagitator 176 including a plate 182 and eight vanes 184 detachablymounted to the plate 182. Also mounted on the plate 182 is a castledpipe 178 having a plurality of slots 180 formed therein on the end ofthe pipe 178 that interfaces with the plate 182. The slots 180 extendthrough the wall of the pipe 178 and are disposed in at leastsubstantially equally radially spaced relation about the center axis ofthe castled pipe 178. The castled pipe 178 has a diameter and length of20 inches (51 cm), and includes 8 of the slots 180 which each are 8inches (20 cm) wide and 7 inches (18 cm) long. Each of the agitators inthe third and fourth compartments has the design as shown in FIG. 8,except without the castled pipe 178. None of these agitators providesthe pumping action desired with the present invention. Oxygen gas is fed60% to the first compartment, 25% to the second compartment, 10% to thethird compartment and 5% to the fourth compartment of the autoclave.Pressure oxidation is conducted at a temperature of from about 190° C.to about 200° C. and a total pressure of about 273 psig (1882 kPa),including an oxygen gas overpressure of about 55 psi (379 kPa). The feedslurry to the autoclave is generally maintained at a slurry density in arange of from about 35% to about 40% solids.

Table 1 presents data from several pressure oxidation processing runsusing mineral material feeds having a variety of sulfide sulfurcontents. As expected, oxygen utilization efficiency tends to drop whenprocessing mineral material feeds having lower sulfide sulfur contents.

TABLE 1 COL 1 COL 11 SULFIDE COL 2 COL 6 COL 8 COL 9 COL 10 OXY- SULFURINLET COL 3 COL 4 COL 5 KLBS COL 7 GOLD SULFUR LBS 02/ GEN RANGE FEEDAVG S = S = (%) OXY- FREE RE- OXIDA- LBS S = UTILI- (%) (TPS) S = %(TPS) ACD GEN ACID COVERY TION OXI. ZATION +7.0 674 7.225 48.7 0.978202.5 10.7 94.95% 86.47% 2.31 82.78% 6.75-6.99 616 6.824 42.0 0.761193.0 9.2 93.11% 88.81% 2.49 76.55% 6.50-6.74 691 6.619 45.8 0.913 203.37.7 91.37% 86.20% 2.46 77.21% 6.25-6.49 666 6.351 42.3 0.819 203.0 9.492.37% 87.08% 2.65 71.81%  6.0-6.24 702 6.118 43.0 0.778 200.7 7.691.20% 87.26% 2.58 74.12% 5.75-5.99 727 5.888 42.8 0.912 203.0 6.690.98% 84.50% 2.70 70.42%  5.5-5.74 740 5.604 41.4 1.070 205.0 5.990.65% 80.86% 2.96 64.87% 5.25-6.49 751 5.372 40.4 1.016 203.7 7.091.18% 81.10% 3.01 63.66%  5.0-5.24 761 5.124 39.0 0.996 204.8 6.590.57% 80.59% 3.16 60.68% 4.75-4.99 745 4.877 36.3 0.904 205.5 7.991.03% 81.48% 3.39 57.00%  4.5-4.74 790 4.624 36.5 0.516 209.3 7.491.81% 88.87% 3.13 61.50% 4.25-4.49 809 4.459 36.1 0.633 208.8 7.491.58% 85.82% 3.31 58.80%  4.0-4.24 839 4.222 35.4 0.542 211.1 8.190.13% 87.34% 3.35 57.58% 3.75-3.99 799 3.881 31.0 0.356 204.5 14.390.84% 90.76% 3.62 54.79%  3.5-3.74 788 3.588 28.3 0.186 183.0 20.196.36% 94.76% 3.25 58.55% 3.25-3.49 867 3.364 29.2 0.712 198.3 16.191.27% 78.87% 4.93 47.99%  3.0-3.24 804 3.171 25.5 0.329 196.1 21.190.46% 90.15% 4.47 46.98% 2.75-2.99 840 2.764 23.2 0.040 188.0 22.093.38% 98.55% 3.90 48.76%  2.5-2.74 788 2.734 21.5 0.037 198.0 15.388.27% 98.65% 4.43 43.00% 2.25-2.49 816 2.390 19.5 0.081 179.2 15.882.66% 96.62% 4.68 41.22% −2.24 1,004 1,960 19.7 0.073 196.6 13.8 72.47%96.09% 5.11 37.60%

EXAMPLE 2

Pressure oxidation is conducted as described in Example 1, except thatthe autoclave is configured so that oxygen gas is introduced into eachof the first and second compartments in the lower portion of each stagein a vertically upward direction from directly below the fluid intake ofthe corresponding agitator, as shown schematically in FIG. 10. Also, anagitator pump of a design a shown in FIGS. 6-7 is used in each of thefirst and second compartments of the autoclave, instead of agitatorshaving the design shown in FIG. 8 as used in Example 1. The agitatorpump in each of the first and second compartments is disposed invertical relation and in axial alignment with the corresponding oxygendischarge line. The feed slurry to the autoclave is generally maintainedat a slurry density of from about 40% to about 45% solids.

Table 2 presents data from several pressure oxidation processing runsusing mineral material feeds having a variety of sulfide sulfurcontents. Compared to Example 1, the use of the agitator pump in thefirst two compartments has significantly increased oxygen utilizationefficiency. Furthermore, a significantly higher average flow of mineralmaterial feed is processed per shift. Particularly, remarkable however,is that the higher throughput is achieved generally withoutdetrimentally impacting pressure oxidation performance, as demonstratedby high sulfide sulfur oxidation levels and high gold recoveries shownin Table 2.

TABLE 2 COL 1 COL 11 SULFIDE COL 2 COL 6 COL 8 COL 9 COL 10 OXY- SULFURINLET COL 3 COL 4 COL 5 KLBS COL 7 GOLD SULFUR LBS 02/ GEN RANGE FEEDAVG S = S = (%) OXY- FREE RE- OXIDA- LBS S = UTILI- (%) (TPS) S = %(TPS) ACD GEN ACID COVERY TION OXI. ZATION +7.0 6.75-6.99 6.50-6.746.25-6.49  6.0-6.24 5.75-5.99 984 5.958 58.6 1.240 206.0 15.5 94.06%79.19% 2.11 90.24%  5.5-5.74 5.25-5.49 1,005 5.351 53.8 1.577 206.8 9.189.89% 70.49% 2.62 73.29%  5.0-5.24 986 5.062 49.9 0.969 209.3 5.789.30% 80.89% 2.47 77.41% 4.75-4.99 897 4.831 43.3 0.684 202.0 9.689.39% 85.87% 2.63 73.89%  4.5-4.74 1,006 4.671 47.0 0.958 207.0 7.288.59% 79.44% 2.66 72.50% 4.25-4.49 1,007 4.381 44.1 0.783 209.7 5.388.89% 82.11% 2.80 68.80%  4.0-4.24 1,016 4.124 41.9 0.679 210.5 5.292.21% 83.51% 2.90 66.45% 3.75-3.99 1,022 3.896 39.8 0.512 209.1 5.892.00% 86.88% 2.92 66.32%  3.5-3.74 980 3.613 35.4 0.285 210.8 8.294.07% 92.14% 3.11 62.23% 3.25-3.49 1,008 3.370 34.0 0.335 211.5 7.093.64% 90.04% 3.31 57.96%  3.0-3.24 934 3.115 29.1 0.255 200.4 7.689.57% 91.99% 3.64 52.95% 2.75-2.99 1,026 2.916 29.9 0.181 203.0 5.892.43% 93.82% 3.45 55.58%  2.5-2.74 1,040 2.520 26.2 0.104 210.0 5.093.61% 95.87% 3.97 47.91% 2.25-2.49 −2.24 984 2.223 21.9 0.112 213.3 4.791.67% 94.75% 5.00 39.16%

EXAMPLE 3

Pressure oxidation is conducted as described in Example 2, except thatthe total mineral material feed is evenly split between the firstcompartment and the second compartment of the autoclave, and oxygen gasis split 46% to the first compartment, 46% to the second compartment, 5%to the third compartment and 3% to the fourth compartment. Also, theflow of mineral material feed is introduced into the first and secondcompartments in an upward direction directed at the correspondingagitator pump, as shown schematically in FIG. 11. Also, an agitator pumpof the design as shown in FIGS. 6-7 is used in each of the fourcompartments. The feed slurry to the autoclave is generally maintainedat a slurry density of around 46% to 47% solids.

Table 3 presents data from several pressure oxidation runs using mineralmaterial feeds having a variety of sulfide sulfur contents.

TABLE 3 COL 1 COL 11 SULFIDE COL 2 COL 6 COL 8 COL 9 COL 10 OXY- SULFURINLET COL 3 COL 4 COL 5 KLBS COL 7 GOLD SULFUR LBS 02/ GEN RANGE FEEDAVG S = S = (%) OXY- FREE RE- OXIDA- LBS S = UTILI- (%) (TPS) S = %(TPS) ACD GEN ACID COVERY TION OXI. ZATION +7.0 6.75-6.99 6.50-6.746.25-6.49  6.0-6.24 5.75-5.99  5.5-5.74 5.25-5.49  5.0-5.24 939 5.12348.09 0.347 203 17.1 93.99% 93.22% 2.16 88.59% 4.75-4.99 1,026 4.86849.92 0.662 208 13.2 95.46% 86.44% 2.33 82.62%  4.5-4.74 1,000 4.67246.72 0.497 212 14.2 95.20% 89.43% 2.47 77.85% 4.25-4.49 881 4.384 38.640.268 207 14.6 95.20% 93.89% 2.78 70.20%  4.0-4.24 956 4.126 39.44 0.348213 13.2 92.05% 91.50% 2.87 67.30% 3.75-3.99 1,111 3.896 43.28 0.422 2086.8 94.58% 89.18% 2.59 75.29%  3.5-3.74 1,078 3.635 39.20 0.340 205 6.794.10% 90.63% 2.75 70.13% 3.25-3.49 1.126 3.368 37.94 0.289 208 5.293.97% 91.41% 2.86 67.79%  3.0-3.24 1,030 3.147 32.41 0.333 202 5.493.61% 89.41% 3.34 57.79% 2.75-2.99 1,063 2.830 30.07 0.284 198 5.795.20% 89.97% 3.51 55.13%  2.5-2.74 2.25-2.49 −2.24

As seen in FIG. 3, oxygen utilization efficiency is generally improvedin relation to the data of Example 2, and sulfide sulfur oxidation andgold recoveries remain high.

A combined summary of data from Examples 1-3 is presented in Table 4.

TABLE 4 COL 10 COL 1 COL 5 COL 7 COL 8 COL 9 OXY- INLET COL 2 COL 3 COL4 KLBS COL 6 GOLD SULFUR LBS 02/ GEN FEED AVG S = S = (%) OXY- FREE RE-OXIDA- LBS S = UTILI- (TPS) S = % (TPS) ACD GEN ACID COVERY TION OXI.ZATION Example 1 757 5.157 39.049 0.835 204 11.4 90.54% 84.23% 3.1262.79% Example 2 1001 3.980 39.846 0.584 209 7.3 91.59% 86.05% 3.0165.00% Example 3 1021 4.005 40.573 0.379 206 10.2 94.24% 90.51% 2.7671.27%

There are a number of notable observations regarding the data presentedin Table 4. One is that the average free acid content in the autoclavedischarge and sulfur oxidation occurring during pressure oxidation arewithin acceptable ranges for all of the Examples. Another is that theratio of the quantity of oxygen gas feed to the autoclave per pound ofsulfide sulfur oxidized is smaller for Example 2 vs. Example 1 and issmaller for Example 3 vs. either Example 1 or Example 2.Correspondingly, the average oxygen gas utilization efficiency is higherfor Example 2 vs. Example 1 and is higher for Example 3 vs. eitherExamples 1 or 2.

The foregoing description of the present invention has been presentedfor purposes of illustration and description. Furthermore, thedescription is not intended to limit the invention to the form disclosedherein. Consequently, variations and modifications commensurate with theabove teachings, and skill and knowledge of the relevant art, are withinthe scope of the present invention. The embodiments describedhereinabove are further intended to explain best modes known ofpracticing the invention and to enable others skilled in the art toutilize the invention in such, or other embodiments and with variousmodifications required by the particular application(s) or use(s) of thepresent invention. It is intended that the appended claims be construedto include alternative embodiments to the extent permitted by the priorart.

The foregoing description of the present invention has been presentedfor purposes of illustration and description. Furthermore, thedescription is not intended to limit the invention to the form disclosedherein. Consequently, variations and modifications commensurate with theabove teachings, and skill and knowledge of the relevant art, are withinthe scope of the present invention. The embodiments describedhereinabove are further intended to explain best modes known ofpracticing the invention and to enable others skilled in the art toutilize the invention in such, or other embodiments and with variousmodifications required by the particular application(s) or use(s) of thepresent invention. It is intended that the appended claims be construedto include alternative embodiments to the extent permitted by the priorart.

The terms “comprise”, “include”, “have” and “contain”, and variations ofthose terms, as may be used to describe features that make up one ormore aspect of the invention and as may be recited in the claims, areintended to indicate only that a particular feature is present to aspecified extent, and are not intended to limit the presence of otherfeatures or the presence of a particular feature beyond the specifiedextent, unless such a limitation is otherwise expressly stated.

What is claimed is:
 1. A method for pressure oxidation of a mineralmaterial comprising at east one sulfide mineral to free at least onemetal value from the sulfide mineral to facilitate recovery of the metalvalue, the method comprising: introducing a feed of the mineral materialin particulate form into a reactor, so that, in the reactor, the mineralmaterial is in a slurry with a liquid; introducing oxygen gas into thereactor to contact the slurry and oxidize at least a portion of thesulfide mineral to thereby free at least a portion of the metal valuefrom the sulfide; and agitating the slurry within the reactor, theagitating comprising drawing into and expelling from a cavity of arotating agitator at least portions of the slurry and the oxygen gas tocycle the portions of the slurry and the oxygen gas through the cavitywith a pumping action, wherein the agitator comprises a vane and atleast a portion of the vane extends outside of the cavity so that duringthe rotating the vane contacts the slurry outside of the cavity.
 2. Themethod of claim 1, wherein: the introducing oxygen gas into the reactorcomprises directing a flow of oxygen gas toward a fluid intake throughwhich the portions of the slurry and the oxygen gas enter the agitatorfor direction to the cavity.
 3. The method of claim 2, wherein: theintroducing the feed of the mineral material into the reactor comprisesdirecting a flow of a feed slurry including the mineral material towardthe fluid intake.
 4. The method of claim 2, wherein: the flow of oxygengas is introduced into the reactor at a location vertically lower thanthe fluid intake.
 5. The method of claim 4, wherein: the flow of oxygengas is introduced into the reactor at a location directly below thefluid intake, and the flow of oxygen gas is directed at the fluid intakein a substantially vertically upward direction.
 6. The method of claim1, wherein: the cavity is defined between first and second spacedpartitions of the agitator.
 7. The method of claim 6, wherein: thedrawing comprises introducing the portions of the slurry and the oxygengas through at least one aperture formed in the first partition.
 8. Themethod of claim 7, wherein: the first and second partitions arevertically spaced, with the second partition at a vertically higherelevation than the first partition; and the introducing oxygen gas intothe reactor comprises directing a flow of oxygen gas into the slurry ata location vertically lower than the first partition, the flow of oxygengas being directed at an upward angle relative to horizontal in adirection toward a fluid intake of the agitator that is in fluidcommunication with the cavity.
 9. The method of claim 8, wherein: theflow of oxygen gas is introduced into the slurry at a location that isno farther than about 12 inches (30 cm) from the fluid intake.
 10. Themethod of claim 9, wherein: the aperture is the fluid intake.
 11. Themethod of claim 8, wherein: the agitator comprises an inlet conduitfluidly interconnected with the aperture and an open end of the inletconduit is the fluid intake.
 12. The method of claim 11, wherein: theflow of oxygen gas is directed at least generally toward a center of thefluid intake along a path that is at least substantially axially alignedwith the inlet conduit.
 13. The method of claim 7, wherein: the agitatorcomprises a plurality of said vane; and the drawing and expellingcomprise rotating the plurality of vanes about an axis of rotation tocreate a fluid suction within the cavity.
 14. The method of claim 13,wherein: the axis of rotation extends through the aperture.
 15. Themethod of claim 14: wherein at least a portion of each of the vanesextends in a vertical direction between the first and second partitionsfrom at least the first partition to at least the second partition. 16.The method of claim 15, wherein: the portion of each of the vanes thatextends in a vertical direction between the first and second partitionsextends generally in a direction from the perimeters of the first andsecond partitions inward toward the aperture.
 17. The method of claim15, wherein: at least a portion of each of the vanes extends in adirection away from the aperture to a location radially beyond aperimeter of each of the first and second partitions.
 18. The method ofclaim 1, wherein: the drawing and expelling comprises rotating at leasta portion of the agitator to create a fluid suction within the cavity.19. The method of claim 1, wherein the introducing the feed of mineralmaterial comprises: introducing at least a first flow of the feed ofmineral material into the reactor at a first location; and introducingat least a second flow of the feed of mineral material into the reactorat a second location spaced from the first location.
 20. The method ofclaim 19, wherein: the reactor is a multi-stage reactor having aplurality of compartments arranged in series with adjacent of thecompartments in series being at least partially separated by a divider;and the introducing at least a first flow comprises introducing thefirst flow of the feed of mineral material into a first compartment inseries of the compartments, and the introducing at least a second flowcomprises introducing the second flow of feed into a second compartmentin series of the compartments.
 21. The method of claim 20, wherein: eachof the first and second compartments has at least one the agitatordisposed therein, and the agitating is executed independently withineach of the first and second compartments.
 22. The method of claim 21,wherein: the introducing oxygen gas into the reactor comprises directinga first flow of oxygen gas into the first compartment and directing asecond flow of oxygen gas into the second compartment.
 23. The method ofclaim 22, wherein: the first flow of oxygen gas is directed at a firstsaid agitator agitating in the first compartment and the second flow ofoxygen gas is directed at a second said agitator agitating in the secondcompartment.
 24. The method of claim 23, wherein: the first flow of feedis directed toward the first agitator and the second flow of feed isdirected toward the second agitator.
 25. The method of claim 20,wherein: the reactor comprises at least a third compartment in series ofthe compartments, wherein all of the mineral material entering the thirdcompartment flows from the second compartment.
 26. The method of claim20, wherein: the first flow of feed is at a first flow rate and thesecond flow of feed is at a second flow rate, the first and second flowrates being substantially the same.
 27. The method of claim 20, wherein:at least a portion of the mineral material in the feed is a whole ore.28. The method of claim 20, wherein: at least a portion of the mineralmaterial in the feed is a sulfide concentrate produced in a flotationoperation.
 29. The method of claim 1, wherein: the metal value comprisesat least one metal component selected from the group consisting ofcopper, nickel, zinc, lead, cobalt, vanadium, tungsten, molybdenum andcombinations thereof.
 30. The method of claim 29, comprising: in thereactor, dissolving at least a portion of the metal component into theliquid; and discharging the liquid from the reactor and thereafterrecovering at least a portion of the metal component from the liquid.31. The method of claim 30, wherein: the recovering comprises at leastone of selective precipitation, ion exchange, solvent extraction andelectrowinning of at least a portion of the metal component.
 32. Themethod of claim 1, wherein the metal comprises gold in association withthe sulfide mineral.
 33. The method of claim 32, comprising: maintainingthe slurry within the reactor at a temperature of at least 160° C. 34.The method of claim 32, wherein: the introducing oxygen gas into thereactor comprises introducing the oxygen gas into the reactor at anoxygen gas overpressure of at least about 10 psi (69 kPa).
 35. Themethod of claim 32, comprising discharging from the reactor an oxidizedslurry and thereafter leaching at least a portion of the gold from solidresidue of the oxidized slurry with a leaching solution including alixiviant for gold.
 36. The method of claim 35, wherein the mineralmaterial comprises at least one metal component selected from the groupconsisting of copper, nickel, zinc, lead, cobalt, vanadium, tungsten andcombinations thereof, the method comprising: in the reactor, dissolvingat least a portion of the metal component into the liquid; andrecovering at least a portion of the metal component from liquid of theoxidized slurry.
 37. The method of claim 36, wherein the recovering themetal component comprises at least one of selective precipitation, ionexchange, solvent extraction and electrowinning of at least a portion ofthe metal component.
 38. The method of claim 37, wherein the metalcomponent comprises copper.
 39. The method of claim 38, wherein therecovering comprises solvent extraction of at least a portion of thecopper.
 40. The method of claim 1, wherein: during the introducing afeed, at least a first flow of the feed is introduced into the reactorat a first location and at least a second flow of the feed is introducedinto the reactor at a second location.
 41. The method of claim 40,wherein: the reactor comprises a plurality of compartments arranged inseries, with adjacent of the compartments in series being at leastpartially separated by a divider; and the first flow is introduced intoa first compartment in series of the compartments, and the second flowis introduced into a second compartment in series of the compartments.42. The method of claim 41, wherein: the agitating is executedindependently within each of the first and second compartments.
 43. Themethod of claim 42, wherein: the introducing oxygen gas comprisesdirecting a first flow of oxygen gas into the first compartment anddirecting a separate second flow of oxygen gas into the secondcompartment.
 44. The method of claim 43, wherein: the first flow ofoxygen gas is directed toward a fluid intake of a first said agitatordisposed in the first compartment and the second flow of oxygen gas isdirected toward a fluid intake of a second said agitator disposed in thesecond compartment.
 45. The method of claim 41, wherein: the reactorcomprises at least a third compartment in series of the compartments,wherein all of the mineral material within the third compartment flowsfrom the second compartment.
 46. The method of claim 40, wherein: thefirst flow of the feed and the second flow of the feed each comprise atleast about 25 weight percent of the feed.
 47. The method of claim 46,wherein: the first flow of the feed comprises at least about 50 weightpercent of the feed.
 48. The method of claim 40, wherein the metal valuecomprises gold.
 49. The method of claim 48, comprising discharging fromthe reactor an oxidized slurry and thereafter leaching at least aportion of the gold from solid residue of the oxidized slurry with aleach solution including a lixiviant for gold.
 50. A pressure oxidationsystem, comprising: a feed system; a reactor comprising: (i) a pressurevessel comprising at least a first inlet, a second inlet and a firstoutlet, wherein the feed system is fluidly interconnected with the firstinlet so that a feed slurry is introducible into the pressure vesselthrough the first inlet; and (ii) at least one rotatable agitator pumpdisposed inside of the pressure vessel, wherein the at least oneagitator pump comprises a drive shaft, a cavity and a pair of verticallyspaced partitions, wherein a first said partition comprises a firstinlet aperture and a second said partition is fixedly interconnectedwith the drive shaft, and wherein the agitator pump further comprises aplurality of vanes extending at least between the first and secondpartitions, wherein at least a portion of one or more of the vanesextends outside of the cavity; and an oxygen supply system fluidlyinterconnected with the second inlet of the pressure vessel.
 51. Thesystem of claim 50, wherein: the first and second partitions aredisposed in at least substantially parallel and horizontal relation; andthe portion of the one or more of the vanes extends beyond a perimeterof at least one of the first and second partitions in a direction atleast generally away from the first inlet aperture.
 52. The system ofclaim 51, wherein: each of the one or more of the vanes has a heightgreater than a spacing between the first and second partitions, whereinat least a portion of each of the one or more of the vanes extendsvertically above at least the second partition.
 53. A pressure oxidationsystem, comprising: a feed system; a reactor comprising: (i) a pressurevessel comprising at least first and second compartments, a first inletto the first compartment, a second inlet to the second compartment, athird inlet, and a first outlet, wherein a first divider at leastpartially isolates the first compartment from the second compartment,and wherein the feed system is fluidly interconnected with each of thefirst and second inlets whereby a feed slurry is simultaneouslyintroducible directly into each of the first and second compartmentsfrom the feed system; and (ii) at least one agitator pump disposed ineach of the first and second compartments, wherein the agitator pumpcomprises a cavity and a plurality of vanes, wherein at least a portionof one or more of the vanes extends outside of the cavity; and an oxygensupply system fluidly interconnected with at least the third inlet tothe pressure vessel whereby oxygen is introducible into the pressurevessel from the oxygen supply system.
 54. A chemical reactor,comprising: a vessel having an interior reactor volume to contain afluid; and at least one rotatable agitator disposed within the interiorreactor volume, the agitator comprising a cavity and a plurality ofvanes, wherein at least a portion of one or more of the plurality ofvanes extends outside of the cavity; wherein, when the agitator issubmerged in a fluid contained within the reactor volume and rotated, afluid suction is created within the cavity and at least portions of thefluid are cycled through the cavity to agitate the fluid.
 55. Thechemical reactor of claim 54, wherein: the agitator comprises a firstpartition and a second partition in spaced relation to the firstpartition; and the cavity is located between the first partition and thesecond partition.
 56. The chemical reactor of claim 55, wherein: atleast a portion of each of the vanes is disposed between the first andsecond partitions.
 57. The chemical reactor of claim 56, wherein: theagitator is rotatable about an axis of rotation that extends through thecavity; and the portion of each of the vanes disposed between the firstand second partitions extends generally in a radially inwardly directionin relation to the axis of rotation.
 58. The chemical reactor of claim57, wherein: the first partition includes at least one aperture throughwhich fluid is introduced into the cavity during operation of theagitator.
 59. The chemical reactor of claim 58, wherein: the secondpartition is connected with a shaft that is rotatable to rotate theagitator.
 60. The chemical reactor of claim 56, wherein: the portion ofeach of the vanes disposed between the first and second partitionsextends at least from the first partition to the second partition. 61.The chemical reactor of claim 56, wherein: the second partition isvertically elevated in relation to the first partition.
 62. The chemicalreactor of claim 54, comprising: at least one first fluid inlet throughwhich a first fluid is introducible into the reactor volume; the firstfluid inlet being configured so that when the first fluid is introducedinto the reactor volume from the first fluid inlet, flow of the firstfluid exiting the first fluid inlet is directed at a fluid intake of theagitator.
 63. The chemical reactor of claim 62, comprising: at least onesecond fluid inlet through which a second fluid is introducible into thereactor volume; the second fluid inlet being configured so that when thesecond fluid is introduced into the reactor volume from the second fluidinlet, flow of the second fluid exiting the second fluid inlet isdirected at the fluid intake.
 64. The chemical reactor of claim 63,wherein: flow of the first fluid and flow of the second fluid intersectin the vicinity of the fluid intake.
 65. The chemical reactor of claim63, wherein: the reactor volume is divided into a plurality ofcompartments arranged in series; at least one of the agitator isdisposed in each of at least two of the compartments; and each of thetwo compartments has at least one of the first fluid inlet.
 66. Thechemical reactor of claim 63, wherein: each of the two compartments hasat least one of the first fluid inlet and at least one of the secondfluid inlet.
 67. A method for pressure leaching at least one metal valuefrom a metal-containing mineral material, the method comprising:introducing a feed of the mineral material in particulate form and aleach liquid into a reactor, so that in the reactor the mineral materialis in a slurry with the leach liquid; in the reactor, dissolving atleast a portion of the metal value from the mineral material into theleach liquid; and agitating the slurry within the reactor, the agitatingcomprising drawing into and expelling from a cavity of a rotatingagitator at least portions of the slurry to cycle the portions of theslurry through the cavity with a pumping action, wherein the agitatorcomprises a plurality of vanes with at least a portion of one or more ofthe vanes extending outside of the cavity, so that during the rotatingthe one or more of the vanes contacts the slurry outside of the cavity.68. The method of claim 67, wherein: the metal value is selected fromthe group consisting of copper, nickel, cobalt, platinum, palladium,gold, uranium, vanadium, tungsten, molybdenum, zinc, manganese andaluminum.
 69. A method for dispersing a material in a flowable medium,the method comprising: introducing a material into a contained volume ofa flowable medium; dispersing the material in the flowable medium, thedispersing comprising drawing into and expelling from a cavity of arotating agitator, disposed within the contained volume of the flowablemedium, at least portions of the flowable medium and the material tocycle the portions through the cavity with a pumping action, wherein theagitator comprises a plurality of vanes and at least a portion of one ormore of the vanes extends outside of the cavity, so that during therotating the one or more of the vanes contacts a portion of the flowablemedium located outside of the cavity.
 70. The method of claim 69,wherein the material comprises a first reactant and the flowable mediumcomprises a second reactant, the method comprising: reacting, in thereactor, at least the first reactant and the second reactant to form atleast one reaction product.
 71. A method for mixing multiple componentsof a flowable medium comprising the components, the method comprising:circulating at least portions of the flowable medium through an agitatorpump at least partially submerged in a contained volume of the flowablemedium; the circulating comprising rotating the agitator pump to createa fluid suction in a cavity of the agitator pump, thereby causing atleast portions of the flowable medium to be drawn into the cavity andexpelled from the cavity with a pumping action, wherein the agitatorpump comprises a plurality of vanes and at least a portion of the one ormore of the vanes extends outside of the cavity, so that during therotating the one or more of the vanes contacts the flowable mediumoutside of the cavity.
 72. The method of claim 15, wherein: at least aportion of each of the vanes extends in a direction away from theaperture to a location radially beyond a perimeter of at least one ofthe first and second partitions.
 73. The method of claim 15, wherein:the first and second partitions are vertically spaced, with the secondpartition at a vertically higher elevation than the first partition; andthe portion of each of the vanes that extends outside of the cavityextends to a location vertically above the second partition.
 74. Themethod of claim 15, wherein: the first and second partitions arevertically spaced, with the second partition at a vertically higherelevation than the first partition; and the portion of each of the vanesthat extends outside of the cavity extends to a location verticallybelow the first partition.
 75. The method of claim 1, wherein: therotating agitator comprises a rotatable drive shaft that extendslongitudinally in a vertical direction.
 76. The method of claim 75,wherein: the cavity is located adjacent a vertically lower longitudinalend of the drive shaft.
 77. The system of claim 52, wherein: each of theone or more of the vanes has a height greater than a spacing between thefirst and second partitions, wherein at least a portion of each of theone or more of the vanes extends vertically below at least the firstpartition.
 78. The system of claim 50, wherein the drive shaft extendslongitudinally in a vertical direction.
 79. The system of claim 78,wherein the cavity is located adjacent a vertically lower longitudinalend of the drive shaft.
 80. The system of claim 50, wherein a portion ofeach of the one or more of the vanes extends beyond a perimeter of eachof the first and second partitions.
 81. The system of claim 50, whereinthe feed system comprises the feed slurry, the feed slurry including atleast an aqueous liquid and a sulfide mineral material in particulateform.
 82. The system of claim 53, wherein the feed system comprises thefeed slurry, the feed slurry including at least an aqueous liquid and asulfide mineral material in particulate form.